Dissertations / Theses on the topic 'Development of polymeric materials'

The possibility to control molar mass and termination of the growing chain is fundamental to create well-defined, reproducible materials. For this reason, in order to apply polydithienopyrrole (PDTP) as organic conjugated polymer, the possibility of controlled polymerization needs to be verified. Another aspect that is still not completely explored is bound to the optical activity of the PDTP, which bearing appropriate substituents may adopt a helical conformation. The configuration of the helix, built up from achiral co-monomers, can be established in an enantiopure way by using only a small percentage of the chiral monomer co-polymerized with achiral co-monomer. The effect, called “sergeants and soldiers effect”, is expressed by the nonlinear increase of the chiral response vs the ratio of the chiral co-monomer used for the polymerization. To date, this effect is still not completely explored for PDTP. In this framework the project will investigate, firstly, the possibility to obtain a controlled polymerization of PDTP. Then, monomers with different side chains and organometallic functions will be screened for a CTCP-type polymerization. Also a Lewis-acid based cationic polymerization will be performed. Moreover the chemical derivatization of dithienopyrrole DTP is explored: the research is going to concern also block copolymers, built up by DTP and monomers of different nature. The research will be extended also to the investigation of optically active derivates of PDTP, using a chiral monomer for the synthesis. The possibility to develop a supramolecular distribution of the polymeric chains, together with the “sergeants and soldiers effect” will be checked investigating a series of polymers with increasing amounts of chiral monomer.

Vascular disease leading to stenotic or occluded arteries and subsequent ischemia is often treated using bypass grafts. Although autologous material, the preferred source for constructing a bypass graft, often provides a graft with satisfactory patency rates, it is not always available and suitable for use. In these cases synthetic material is often utilised but these rarely produce the patency of autologous material. The causes of their failure are compliance mismatch and thrombus formation. For this reason, polyurethane was studied as a suitable graft material due to its compliant nature and excellent thromboresistance. Investigations into the effect of the material stiffness and potential to allow adsorption of blood-borne proteins were conducted, showing that an optimum combination of the two existed for the migration of vascular tissue onto the graft. As this migration can lead to restenosis and reocclusion of a graft, the ability to control the migration rate could limit the failure of the graft through these processes. The electrospinning technique was utilised to develop a polyurethane processing method for producing fibrous materials which better replicate the geometry of the native vessel than do other materials commonly used. The effect of this fibrous structure was to maintain the differentiated state of the vascular cells resident upon it. This contractile state is consistent with that in which cells are found in a healthy vessel and is the opposite state to that of the synthetic phenotype in which cells are found when on planar surfaces in vitro and in diseased vessels. It therefore follows that the control of the phenotypic state can prevent the dedifferentiation of the cells into the synthetic state, whereupon they form a thickening of the vessel wall which, again, ultimately results in restenosis. Mechanical deformation of these electrospun materials was conducted in a dynamic system, replicating the motion in the vascular system in vivo. The effect of this dynamic system was to further develop the degree to which the cells demonstrated a contractile phenotype. This highlights that the electrospun polyurethane graft material represents a promising alternative to those commonly used, perhaps due to it somewhat recapitulating the topographical and mechanical nature of the native vessel.

Doutoramento em Biologia<br>Bacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. Therefore, the scientific community is currently searching for new solutions to fight bacteria and infectious diseases, without promoting antimicrobial resistance. One of the most promising strategies is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. At the same time that bacterial population grows, the concentration of AIs in the bacterial environment increases. When a threshold concentration of AIs is reached, bacterial cells respond to it by altering their gene expression profile. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QSphenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should to be able to adsorb bacterial signal molecules, limiting their availability in the extracellular environment, with expected disruption of QS. Linear polymers were composed by one of two monomers (itaconic acid and methacrylic acid), which are known to possess strong interactions with the bacterial signal molecules. Molecularly imprinted polymer nanoparticles (MIP NPs) are particles with recognition capabilities for the analyte of interest. This ability is attained by including the target analyte at the synthesis stage. Vibrio fischeri and Aeromonas hydrophila were used as model species for the study. Both the linear polymers and MIP NPs, tested free in solutions and coated to surfaces, showed ability to disrupt QS by decreasing bioluminescence of V. fischeri and biofilm formation of A. hydrophila. No significant effect on bacterial growth was detected. The cytotoxicity of the two types of polymers to a fibroblast-like cell line (Vero cells) was also tested in order to evaluate their safety. The results showed that both the linear polymers and MIP NPs were not cytotoxic in the testing conditions. In conclusion, the results reported in this thesis, show that the polymers developed are a promising strategy to disrupt QS and reduce bacterial infection and resistance. In addition, due to their low toxicity, solubility and easy integration by surface coating, the polymers have potential for applications in scenarios where bacterial infection is a problem: medicine, pharmaceutical, food industry and in agriculture or aquaculture.<br>Infeções bacterianas são um problema recorrente para a saúde pública. A maioria das infeções bacterianas tem aumentado devido ao facto das bactérias se tornarem resistentes aos antibióticos. A procura de estratégias para combater este facto, sem promover a resistência antimicrobiana, tem sido incessante. A atenuação ou até mesmo a disrupção do Quorum Sensing (QS), é uma estratégia promissora para enfrentar este problema. QS é um sistema de comunicação bacteriana, onde há produção e libertação de moléculas sinais específicas, denominadas de Auto Indutores (AIs) para o ambiente. Á medida que a população bacteriana aumenta, aumenta também a concentração de moléculas sinais no ambiente. Quando a concentração destas moléculas atinge um certo limite, há uma alteração a nível da expressão genética. A expressão de determinados genes relacionados com fatores de virulência, produção de toxinas, resistência a antibióticos e formação de biofilmes é intrinsecamente relacionada com QS. Neste estudo foram desenvolvidos dois tipos de polímeros (polímeros lineares e nanopartículas impressas molecularmente) com capacidade para atenuar QS. Ambos os polímeros têm como finalidade a absorção e consequente remoção de moléculas sinais do ambiente, com consequente disrupção de QS. Os polímeros lineares são compostos por dois tipos de monómeros (ácido itacónico e ácido metacrílico) que possuem afinidade para as moléculas sinais. Nanoparticulas impressas molecularmente são partículas específicas para o alvo de interesse, pois este é incluído no processo de síntese. Vibrio fischeri e Aeromonas hydrophila foram os microrganismos escolhidos para este estudo. A eficiência dos polímeros lineares e das nanopartículas foi testada quer em solução quer como revestimento de superfícies, evidenciando as suas capacidade de disrupção de QS através da diminuição da bioluminescência de V. fischeri e da formação de biofilme de A. hydrophila. O crescimento bacteriano não mostrou ser afetado pela presença destes materiais. A citotoxicidade foi avaliada, usando uma linha celular de fibroblastos, de modo a avaliar a biocompatibilidade. Os resultados mostraram que ambos os materiais não são citotóxicos. Em conclusão, este estudo demonstrou que os polímeros desenvolvidos podem ser uma estratégia efetiva de disrupção de QS e redução de infeções e de resistência bacteriana. Devido às suas características, reduzida citotoxicidade, solubilidade e facilidade de integração, estes materiais poderão ser aplicados de diversas formas, especialmente onde há predominância de infeções bacterianas, como ambientes clínicos, farmacêuticos, indústria alimentar, agricultura ou aquacultura.

Bacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. A new solution to fight bacteria and infectious diseases, without promoting antimicrobial resistance, is required. A promise strategy is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QS- phenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should be able to adsorb bacterial signal molecules, limiting their availability in the extracellular environment, with expected disruption of QS. Linear polymers were composed by methyl methacrylate as backbone and itaconic acid or methacrylic acid as functional monomer. IA and MAA monomers were identified by computer modelling to have strong interactions with the AIs produced by Gram-negative bacteria. Cont/d.

The adsorption and separation of platinum(IV) and palladium(II) chlorido species (PtCl₆²⁻ and PdCl₄²⁻) on polystyrene-based beads and nanofibers as well as silica microparticles functionalized with polyamine centres derived from ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) is described. The functionalized sorbent materials were characterized by using microanalysis, SEM, XPS, BET and FTIR. The nanofiber sorbent material functionalized with ethylenediamine (F-EDA) had the highest loading capacity which was attributed to its high nitrogen content (10.83%) and larger surface area (241.3m²/g). The adsorption and loading capacities of the sorption materials were investigated using both the batch and column studies in 1 M HCI. The adsorption studies for both PtCl₆²⁻ and PdCl₄²⁻ on the polystyrene-based sorbent materials fit the Langmuir isotherm while the silica-based sorbents fitted the Freundlich isotherm with R² values > 0.99. In the column experiment the highest loading capacity of Pt and Pd were 7.4 mg/g and 4.3 mg/g respectively on the nanofiber sorbent material based on ethylenediamine (EDA). The polystyrene and silica-based resins with triethylenetetramine (TETA) functionality (M-TETA and S-TETA) showed selectivity for platinum and palladium, respectively. Metal chlorido complexes loaded on the sorbent materials were recovered by using 3% m/v thiourea solution as teh eluting agent with quantitative desorption efficiency under the selected experimental conditions. The separation of platinum from palladium was partially achieved by selective stripping of PtCl₆²⁻ with 0.5 M of NaClO₄ in 1.0 M HCI with PdCl₄²⁻ was eluted with 0.5 M thiourea in 1.0 M HCI. The selectivity of the M-TETA and S-TETA sorbent materials was proved by column separation of platinum(IV) and palladium(II), respectively, from synthetic solutions containing iridium(IV) and rhodium(III). The loading capacity for platinum on M-TETA was 0.09 mg/g while it was 0.27 mg/g for palladium on S-TETA.<br>Acrobat PDFMaker 10.1 for Word<br>Adobe Acrobat 9.54 Paper Capture Plug-in

Thesis (PhD) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.<br>A thesis submitted for the degree of Doctor of Philosophy, Industrial Research Institute Swinburne, Swinburne University of Technology - 2006. Typescript. "August 2006". Includes bibliographical references (p. 361-389).

El desenvolupament de diferents materials per a les tècniques d’extracció mitjançant processos de sorció és una àrea en continua expansió; no obstant, l’extracció d’anàlits polars encara és un tema que requereix més investigació. En aquesta Tesi s’han desenvolupa nous materials que reuneixen de selectivitat i/o capacitat característiques per a extreure contaminants orgànics polars en mostres aquoses. La primera part descriu el desenvolupament de nous materials polimèrics que milloren la capacitat i selectivitat de l’extracció en fase solida, i hi inclau els polímers altament entrecreuats amb caràcter hidrofílic, els sorbents altament entrecreuats d’intercanvi iònic de mode-mixte i els líquids iònics suportots en fases polimèriques; així com la seva avaluació com a nous sorbents per a la extracció de contaminats polars en diferents mostres aquoses mediambientals seguit de l’anàlisi per LC. La segona part está centrada en la preparació de noves barres agitadores amb recobriments monolítics polars i la seva posterior aplicació per l’extracció d’analits polars en diferents aigües de procedéncia mediambiental.<br>The development of different materials for sorptive extraction techniques is a continuously evolving field of research. Although there have been significant developments in this area, the extraction of polar analytes is still considered the bottleneck of the extraction process. The efforts have been undertaken to improve capacity and selectivity. For this reason, one of the main objectives of this Thesis is to develop new materials to extract polar organic contaminants from water samples. The first part reports on the development of new polymeric materials for solid-phase extraction including hypercrosslinked polymers with hydrophilic character, mixed-mode ion-exchange hypercrosslinked sorbents and supported ionic liquid polymeric phases and their evaluation as SPE sorbents for the extraction of polar contaminants, followed by LC analysis. The second part is focused on the preparation of new stir bars with polar monolithic coatings and their application to stir bar sorptive extract polar analytes from environmental water samples.

This thesis addresses the processing, morphology, mechanical properties, and acoustic properties of new polymeric foam materials. A batch foaming process, a rotational mold foaming process and a constrained mold foaming process were designed and applied in the producing of polymeric foams. Microcellular closed cell polymethyl-methacrylate (PMMA) foams were produced using the batch foaming process. The foam morphologies and mechanical properties such as elastic modulus, tensile strength and elongation at break were investigated by varying the foaming parameters. The PMMA microcellular foam showed superior mechanical properties in tensile strength and elongation at break over conventional foams. Nanoclay was used as reinforcement filler and a nucleation agent for PMMA in the batch foaming process. The nanoclay affected the foaming behavior and enhanced the mechanical properties of the microcellular PMMA foams. The PMMA nanocomposite foam with 0.5 wt % nanoclay exhibited optimized mechanical properties. Fine celled Polypropylene (PP) and low density Polyethylene (LDPE) foams were also produced using the rotational mold foaming. The processing parameters such as the particle sizes and processing time were important parameters in this process. The obtained PP foam exhibited a greatly improved energy absorption capacity. Opened cell PMMA foams were produced using a particulate leaching/gas foaming method for acoustic absorption applications. The foam morphology i.e. porosity and cell sizes were independently controlled by altering the processing settings. Consequently, the acoustic performance of the foams was manipulated. Finite element analysis was then employed to predict the macroscopic properties of polymeric foams correlated to their microstructure. The predicted elastic responses of both opened cell and closed cell foams showed great agreement with experimental results.

Dissertation (Ph.D.)--University of Toledo, 2007.<br>Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Engineering." Bibliography: leaves 200-205.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 184-194).<br>Limiting the use of fossil fuels is vital to stemming climate change. Incorporation of renewable energy technologies into the grid, and the shift to electric vehicles for transportation increases the need for better energy storage media. Lithium-air (O₂) batteries are of great interest because they have high theoretical energy densities. However, conventional Li-O₂ batteries face challenges such as the use of volatile and flammable liquid electrolytes, side reactions between the electrolyte/electrode with oxygen reduction products, and high charging over-potentials that lead to poor cycle life. We address these challenges by developing non-flammable polymeric-based electrolytes and electrodes, and investigate their performance and stability in Li-O₂ batteries. In this thesis, we synthesized and studied the properties of a nonvolatile and nonflammable siloxane solid polymer electrolyte that can support Li-O₂ discharge, but show it is vulnerable to reaction with the desired Li2O₂ discharge product. We developed a screening tool that involves mixing commercial Li2O₂ with various polymers of interest for Li-O₂ batteries, and formulate polymer reactivity rules where the presence of electron-withdrawing groups on the polymer and adjacent hydrogen atoms make the polymer vulnerable to degradation. Of the polymers studied in contact with Li2O₂, poly(methyl methacrylate) was found to be stable, and then used as part of a gel polymer electrolyte with an ionic liquid (IL) and lithium salt. The Li/IL molar ratio in the GPE was shown to allow for a switch from a 2 e- to 1e- oxygen reduction chemistry, and the formation of ionic liquid-superoxide complexes as the discharge product. Exploiting this understanding of the influence of a bulky ionic liquid cation on the oxygen electrochemistry, we incorporate ammonium salts in a Li-O₂ battery and show it can also support discharge and lead to > 0.5 V reduction in charging overpotential when compared to lithium salts. Finally, we explore an electron conducting polymer electrode poly(3, 4- ethylenedioxythiophene) (PEDOT) as a Li-O₂ electrode and show the polymeric surface allows for oxygen reduction and Li2O₂ formation. Coupling fundamental understanding with material selection can empower the design of next generation Li-O₂ batteries.<br>by Chibueze Vincent Amanchukwu.<br>Ph. D.

L’adsorption de protéines adhésives telles que la fibronectine (Fn) à la surface d’un dispositif médical suivant son introduction dans le corps joue un rôle critique dans la réponse biologique. Afin de moduler cette réponse, la création de revêtements bioactifs à la surface des matériaux représente une stratégie à adopter. Dans ce contexte, ce projet de recherche vise à développer des revêtements capables de promouvoir des interactions cellulaires spécifiques. Ainsi, des revêtements de fibronectine ont été développés à la surface de polymères présentant un potentiel pour être utilisés comme biomatériau : le film de fluorocarbone (CFx) et des polyetherurethanes (PEUs) à surface modifiée. Le film de CFx est un nano-recouvrement déposé par traitement plasma sur l’acier inoxydable, et a été développé pour éviter la corrosion du métal lors d’un contact à long terme avec le sang. Les modifications surfaciques des PEUs ont quant à elles montré leur capacité à réduire l’adhérence plaquettaire par l’ajout d’oligomères fluorés au PEU de base, ou à promouvoir l’adhérence cellulaire, par l’ajout d’oligomères anioniques. La stabilité de revêtements de fibronectine adsorbée ou greffée à la surface de CFx a tout d’abord été analysée sous différentes contraintes (déformation, condition statique et sous flux). Les résultats ont révélé une homogénéité plus importante pour la Fn greffée que pour l’adsorbée. Les essais biologiques effectués par la suite sur les PEUs ont indiqué que la fibronectine jouait un rôle majeur dans la coagulation sanguine et dans l’activation des cellules inflammatoires. Par conséquent, ce projet de recherche a permis de mieux comprendre les mécanismes d’interaction entre la Fn et la surface des polymères. La pertinence du développement de revêtements stables à la surface de matériaux destinés à être en contact avec le sang et de leur rôle dans l’interaction cellulaire a été mise en évidence comme pouvant influencer la cicatrisation et le succès des implants.<br>After the introduction of a medical device into the body, adhesive proteins such as fibronectin (Fn) adsorb to the surface of the material and play a critical role in the mediation of biological responses. To modulate these responses, one strategy consists in developing bioactive coatings at the surface of materials. With the aim of promoting cell interactions, this research project focuses on developing fibronectin coatings on different polymeric materials, which presented suitable properties for blood-contacting applications: fluorocarbonated film (CFx) and surface-modified polyuetherurethanes (PEUs). The CFx film is a nano-coating deposited by plasma treatment on stainless steel substrates developed in order to avoid metal corrosion after long-term blood contact. The PEUs surfaces are modified by oligomer blending: a fluorinated oligomer, reducing platelet adhesion, or an anionic one, promoting cell adhesion, were selected for their ability to modulate cell responses. Firstly, fibronectin was adsorbed or grafted on CFx and characterized under different constraints (plastic deformation, static conditions, and under pseudo-physiological fluid flow). The interaction of fibronectin with the CFx nano-coating enabled to evaluate the stability of the coatings and to validate the relevance of their development. The results revealed greater homogeneity for grafted Fn compared to adsorbed Fn. The influence of Fn adsorption on the surface-modified PEUs towards the response of inflammatory cells and the thrombogenic nature of the surfaces were then investigated. The biological tests indicated that fibronectin played a prominent role in thrombus formation and showed differentiated effect on inflammatory cell activity when coated onto the different polymeric substrates. This research increased our knowledge on the surface interactions between Fn and polymers. The relevance for the development of stable biomolecule coatings at the surface of materials for blood-contacting applications and regarding the role of biomolecule coatings on subsequent cell interactions was shown and focused on the possible influence of the wound healing process and on the final outcomes of implants.

In the field of smart materials for photovoltaic (PV) industry and Organic Electronic (OE), polymeric films that exhibit modular wetting properties and conductive features are considered very promising for several applications. Self-cleaning films for the covering of photovoltaic cells and conductive polymer films are two important examples. The present work is related to the use of Sulfonated Polyarylethersulfone (SPES) for two different applications: i) for PV industry, as flexible and transparent polymeric film having both hydrophilic and hydrophobic features; ii) in the research area of OE, as doping agent for both electrical conductive and polymeric films, and screen printer inks. Polymers based on Polyarylethersulfones (PESs) are favorable materials for preparing membranes for several applications due to their excellent thermal and chemical stability, ion exchange properties, oxidation resistance as well as good mechanical behavior. PES-based membranes have been widely used in advanced separation technologies, including low-cost alternatives to expensive fluorinated polymers in fuel cells, in biomedical fields (as medical devices for blood purification and dialysis) and in food industry as membranes for wine, water and fruit-juices purification. In order to diversify membrane properties and therefore widen possible application fields, chemical modifications of PES matrices can be studied; such modifications can be achieved by supplying different functional groups on the polymer matrix, i.e. sulfonic (-SO3-), hydroxyl (-OH), carboxyl (-COOH) and amino (-NH2) moieties. SPES has received great attention in the last decade due to the possibility to improve the wetting properties of PES membranes thanks to the incorporation of sulfonic groups. This allowed the development of SPES membranes as advanced materials for a variety of separation processes, such as ion exchange, reverse osmosis and electro dialysis process; in all these fields, materials with highly hydrophilic behavior are requested. SPESs can be prepared via two polymerization routes, either via post-sulfonation reaction with different sulfonating agents and solvents of the pre-formed PES polymer -heterogeneous synthesis-, or starting from pre-sulfonated monomers -homogeneous synthesis-. Although homogeneous synthesis allows an easy control of the degree of sulfonation (DS) of the resulting polymer and to avoid side and degradations reactions, heterogeneous synthesis is widely used, both in the industrial and academic area, due to its simplicity and low cost. i) SPES films characterized by both hydrophobic and hydrophilic behavior. In this work, a series of SPESs with different DS were synthesized via homogeneous synthesis starting from 4,4’-difluorodiphenylsulfone, 4,4’–dihydroxydiphenyl and a sulfonated comonomer, 2,5-dihydroxybenzene-3-sulfonate potassium salt (sulfonated hydroquinone in potassium salt). The macromolecular structure was determined via 1H NMR and 1H-1H COSY spectroscopy and the presence of sulfonic groups was confirmed by Fourier Transform Infrared (FT-IR) spectra; the real DS values of SPESs were determined by 1H NMR calculations and confirmed by potentiometric tritation data. Intrinsic viscosities were measured using dimethylacetamide (DMAc) as solvent with and without lithium bromide (LiBr) solution in order to investigate polyelectrolyte effect on SPES samples. The effects of DS increasing on the thermal properties of SPES membranes obtained via solvent casting deposition in DMAc were studied by Thermogravimetric (TGA) analyses and Differential Scanning Calorimetry (DSC); wetting features were investigated by static water contact angle (SWCA). Wettability measurements are commonly used to characterize the relative hydrophilicity or hydrophobicity of a polymer surface; here, in order to investigate the wetting properties of SPES membranes, SWCA measures for all the samples, obtained from solution casting in DMAc, were performed. The samples were solution casted onto a PTFE mold; the wetting features of the membranes were measured both at the air-side and at the PTFE-side surface. Table I shows the results obtained. Sample DS (meq SO3-*g-1) (1H NMR) θw (air-side) θw (PTFE-side) SPES_0.5 0.48 (65) ̅±2 (89) ̅±1 SPES_0.75 0.70 50±2 (85) ̅±1 SPES_1 0.98 (43) ̅±1 (81) ̅±2 Table I. Static water contact angles of samples synthesized. The results reported indicate that the hydrophilicity of SPES membranes improves as -SO3-K+ amount in the SPES membranes increases, due to the high polarity of the -SO3- groups. It is important to underline that, thanks to a direct sulfonation reaction of, the hydrophilic properties of SPES samples are greatly enhanced using low amounts of sulfonic groups. The increase of θw observed on the PTFE-side for SPES membranes with respect to the air-side is due to the different organization of the SO3-K+ groups of the polymeric chains occurring during the evaporation of the solvent, as confirmed by FT-IR spectra performed on both air-side and PTFE one of the polymeric films. Standard materials used as photovoltaic cells cover are characterized by an internal hydrophilic side, optimal for the deposition on solar cells and by an external hydrophobic or hyper-hydrophobic side, designed ad hoc as protective self-cleaning layer from pollution. To improve the hydrophobic properties, the use of SPESs can be very advantageous in fields where hydrophilic/hydrophobic properties can be modulated; moreover, the use of Ionic Liquids (I.Ls.) combined with SPES can be a way to create tailor-made hydrophobic materials for solar cells covering. I.Ls., a class of molten salts, have excellent thermal stability and their physical-chemical properties can be modulated changing the nature of the cation or anion. Modulating cationic apolar groups can dramatically influence the tendency of I.L. towards efficient ion packing and, in turn, its hydrophobic features, e.g. the longer the alkyl chains, the more hydrophobic the salt. The wetting properties of SPES could therefore be modulated by introducing different cationic apolar groups through a novel ionic exchange reaction between the K+ cation of the sulfonic moiety of SPES and the cation of an I.Ls.. The structure of I.Ls. used are reported in Figure I. Figure I. Ionic Liquids used for the cation exchange reactions with SPES. The hydrophobic properties of SPES treated with I.Ls. were found to improve with the DS of sulfonation of SPES, i.e. with the number of K+ ions available for substitution by I.Ls. cations, obtaining contact angles up to (131) ̅° (Table II) leading to self-cleaning surfaces (Figure II). Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses for SPESs and SPES_I.Ls. samples were performed in order to clarify the influence of I.Ls. on the surface properties of the polymeric membranes prepared. Figure III presents SEM morphologies of representative membranes from both air-side and PTFE-side of SPESs and SPES_I.Ls. samples. In the case of SPES_1, no surface differences are detectable between the air-side (IIIa) and the mold-side of the polymeric membrane (IIIb). When I.Ls. are added, it is possible to observe that the surface at the air-side remains smooth (IIIc), while the surface at the mold-side of the membrane changes from smooth to rough (IIId). The roughness of PTFE-side of SPES_I.Ls. membranes increases as the DS of SPESs increases, i.e. with the number of hydrophobic I.Ls. cations exchanged, as it is possible to observe comparing SPES_MEIM_0.5 (IIId) with SPES_MEIM_0.75 (IIIe) and SPES_MEIM_1 (IIIf), and it enhances as the length of the imidazolinium alkyl chains enhances, as shown in Figure IIIf for SPES_MEIM_1, in Figure IIIg for SPES_BBIM_1, in Figure IIIh for SPES_MOIM_1 and in Figure IIIi for SPES_BOIM_1. Samples θw (air-side) θw (PTFE-side) SPES_MEIM_0.5 (86) ̅±2 (108) ̅±1 SPES_MEIM_0.75 (85) ̅±1 (116) ̅±1 SPES_MEIM_1 (89) ̅±1 (121) ̅±1 SPES_BBIM_0.5 (88) ̅±1 (123) ̅±1 SPES_BBIM_0.75 (84) ̅±2 (124) ̅±2 SPES_BBIM_1 (81) ̅±2 (126) ̅±1 SPES_MOIM_0.5 (77) ̅±1 (124) ̅±1 SPES_MOIM_0.75 (80) ̅±1 (125) ̅±2 SPES_MOIM_1 (81) ̅±1 (128) ̅±1 SPES_BOIM_0.5 (85) ̅±1 (130) ̅±1 SPES_BOIM_0.75 (80) ̅±1 (131) ̅±1 SPES_BOIM_1 (81) ̅±1 (131) ̅±1 Table II. Static water contact angles of samples synthesized. . Figure II. Self-cleaning SPES films. Comparing AFM topographies of the mold-side of pristine SPES (Figure IVa) and SPES_I.Ls. samples (Figure IVb, c, d, f, g and h), it is clear that the surfaces of SPES_I.Ls. are much rougher than the surface of SPES sample without I.Ls. When I.Ls. are present, it is possible to observe that the surface at the air-side of the membrane remains smooth (IVe). Conversely, the surface at PTFE-side changes from smooth to rough (IVd); Root-mean-square (RMS) roughness data range from 66.65 nm for the air-side to 185.15 nm for its PTFE- mold side. The roughness of PTFE-side of SPES_I.Ls. membranes increases as the DS of SPESs increases, as it is possible to observe comparing SPES_MEIM_0.5 (IVb) with SPES_MEIM_0.75 (IVc) and SPES_MEIM_1 (IVd). This behavior was confirmed by RMS roughness values that for SPES_MEIM_0.5, SPES_MEIM_0.75 and SPES_MEIM_1 are 101.01 nm, 163.87 nm and 185.15 nm, respectively. The influence of I.Ls. characterized by difference length of the imidazolinium alkyl chains was also investigated and the results obtained suggest that the roughness of the mold-side of SPES_I.Ls. membranes increases as the length of the imidazolinium alkyl chains increases, as shown in Figure IVe for SPES_MEIM_1 -RMS of 185.15 nm-, in Figure IVf for SPES_BBIM_1 -RMS of 192.78 nm-, in Figure IVg for SPES_MOIM_1 -RMS of 206.34 nm- and in Figure IVh for SPES_BOIM_1 -RMS of 236.85 nm-. All AFM images and RMS roughness values obtained agree well with both SWCA data -i.e. the higher the contact angles, the rougher the surface- and SEM analyses, as previously shown in Figure III, confirming that the hydrophobic imidazolinium alkyl chains, orienting themselves during the evaporation of the solvent towards the mold surface, change the membrane surface in correspondence of PTFE-side from smooth to rough. Figure III. (a) SPES_1 air-side; (b) SPES_1 PTFE-side; (c) SPES_MEIM_0.5 air-side; (d) SPES_MEIM_0.5 PTFE-side; (e) SPES_MEIM_0.75 PTFE-side; (f) SPES_MEIM_1 PTFE-side; (g) SPES_BBIM_1 PTFE-side; (h) SPES_MOIM_1 PTFE-side and (i) SPES_BOIM_1 PTFE-side. Figure IV. (a) SPES_1 PTFE-side; (b) SPES_MEIM_0.5 PTFE-side; (c) SPES_MEIM_0.75 PTFE-side; (d) SPES_MEIM_1 PTFE-side; (e) SPES_MEIM_1 air-side; (f) SPES_BBIM_1 PTFE-side; (g) SPES_MOIM_1 PTFE-side and (h) SPES_BOIM_1 PTFE-side. ii) SPES as dopant agent for both electrical conductive and polymeric films and screen printer inks. OE based on polymers is a research field that is gaining more and more interest, both from an academic and an industrial point of view. Organic conductive materials could open several possibilities in the production of new advanced electronic devices: in fact, these materials can conjugate useful features such as flexibility, transparency, durability and lightness typical of polymers, with conductive properties, conferred by highly conjugated organic systems. Polycarbonate (PC) is a polymer characterized by high durability and mechanical resistance, coupled with good thermal properties. One of the most valuable features of PC relies on its extremely good optical behavior: PC is often used as a substitute of glass because the refractive index of the two materials is very similar (1.5237 for glass and 1.5856 for PC at λ = 580 nm) but PC has higher mechanical properties, is lighter and is not fragile. Within this context also Polymethyl Methacrylate (PMMA) is an optimal material for transparent layers (PMMA = 1.4910 at λ = 580 nm) and its monomers can be easily functionalized. The goal of this project was to develop an innovative material bearing at the same time carbonate moieties, useful for optical features, and acrylate groups, functionalized with conductive molecules, in order to obtain transparent conductive films. At first Polyallyl carbonate homopolymers were successfully synthesized through free radical polymerization (NMR, Gel Permeation Chromatography (GPC) and thermal studies were performed). As result of homopolymerization kinetics, it seems that the radical of the propagating species is a stable “pseudo-living” radical, able to initiate the growth of another polymeric chain characterized by conductive functionalities, in order to obtain block copolymers with high molecular weights and conductive continuity along the chain. Acrylate monomers based on conductive molecules were synthesized; the organic molecules used are based on highly aromatic structure, Fluorene Bisphenol, known as “cardo structure”. The high level of electronic delocalization given by the aromatic groups guarantees not only the conductivity, but also high thermal resistance. Polyallyl carbonate and functionalized PMMA block copolymers were indeed successfully synthesized (Figure V) and fully characterized by NMR, GPC and thermal characterizations. Starting from this new material, a transparent polymer film was obtained through solvent casting deposition. In order to improve the conductive features of this material, functional end-capped conducting 3,4-ethylene dioxy thiophene (EDOT) oligomers were synthesized. In particular, EDOT is the monomer adopted for the polymerization of Poly(3,4-ethylene dioxy thiophene) (PEDOT) oligomers, a famous commercial conductive polymer -known as Baytron®- usually doped with Sulphonated Polystyrene (PSS), that it is insoluble in the common organic solvent and therefore difficult to process. In the present work a synthetic route able to enhance PEDOT solubility and conductivity was developed. Methacrylate-terminated PEDOTs were successfully synthesized via oxidative polymerization of EDOT and cross-linkable methacrylate end-capped EDOT, with ferric sulfate as oxidant (Figure VI). EDOT end-capping monomer was prepared through Friedel Crafts acylation starting from EDOT and methacryloyl chloride. The chemical structure and the degree of polymerization of the end-capped PEDOTs were determined by 1H NMR spectroscopy. Figure V. Block copolymers of Polyallyl carbonate and functionalized methacrylic polymers. End-capped PEDOTs have excellent solubility in several organic and chlorinated solvents. Furthermore, the use of cross-linkable end-caps makes EDOT-based oligomers soluble in organic and chlorinated solvents; the cross-linking of PEDOT film is then possible after UV exposure. In order to improve PEDOT conductive properties, the dopant agents based on sulfonic groups commonly used with PEDOT are 2-Naphthalenesulfonic acid, paratoluene sulfonic acid or others. Besides these molecules, also SPES, obtained as reported previously, can be used as dopant agent thanks to both the charge separation deriving from the use of the pre-sulfonated comonomer and the possibility to modulate the moieties of sulfonic groups in the polymeric chains. Figure VI. Synthetic route for methacrylate end-capped PEDOT. Figure VII. SPES as dopant agent for methacrylate end-capped PEDOT. In this work, the oxidative polymerization of EDOT and functional end-capped EDOT monomers with ferric sulfate as oxidant and SPES as dopant was performed (Figure VII); it was found that PEDOT conductive features increase as SPES DS increases reaching 210 S/cm, a value 50 S/cm far higher than the one of commercial PEDOT (160 S/cm). The cross-linking of end-capped PEDOT with the block copolymers of Polyallyl carbonate and functionalized methacrylic polymers, through the vinyl functionalities, in then possible after UV exposure.

Comme je suis particulièrement intéressé par les nanosciences et les nombreuses applications des nanotechnologies, je me suis penché sur le développement de méthodes de fabrication de nanoparticules ultra-petites dont les fonctions peuvent être ajustées avec précision. Récemment, une nouvelle technologie appelée « technologie d’une seule chaîne », c’est-à-dire qui utilise une seule chaîne polymère, est devenue un sujet de recherche de plus en plus motivant pour la communauté scientifique. Cette technologie a l’avantage de dépendre d’une méthode facile de préparation de nanoparticules polymères d’une seule chaîne (SCNPs) et ayant des dimensions typiques de 1,5 à 20 nm. Leurs tailles ultra petites leur confèrent des propriétés spécifiques, ce qui permet de les utiliser comme capteurs, systèmes catalytiques, revêtements à faible viscosité, nanoréacteurs ou pour des applications biomédicales. Grâce aux contributions de nombreux scientifiques durant la dernière décennie, les méthodes de synthèse des SCNPs sont devenues très variées et représentent une technologie désormais mature. Néanmoins, de nombreux problèmes sont à résoudre dans ce domaine, ce qui permettra d’ajouter de nouvelles fonctions ou de les valoriser pour de nouvelles applications. Les polymères sensibles à plusieurs stimuli sont une classe de matériaux intelligents dont les propriétés peuvent être modifiées par l’application d’un stimulus extérieur. Ils sont utilisés extensivement dans les domaines énergétique et biomédical. Comme leurs propriétés physiques et chimiques peuvent être modifiées aisément et efficacement par un contrôle de leur environnement externe, ces polymères sont des candidats pour fabriquer de nouvelles SCNPs. Dans cette thèse, nous nous sommes intéressés au développement de SCNPs ayant de multiples fonctionnalités car cela permet d’ouvrir la voie pour de nouvelles applications. Pour cela, de nombreux polymères sensibles à plusieurs stimuli ont été préparés comme précurseurs à des SCNPs. En concevant spécifiquement ces polymères, il fut possible d’ajouter leurs propriétés de réponse à des stimuli dans les systèmes SCNPs. Le cœur même de cette thèse consiste en trois projets qui utilisèrent trois classes de SCNPs provenant de polymères sensibles aux stimuli. Grâce à leur réponse à plusieurs stimuli, ces SCNPs remplirent de nombreuses fonctions et subirent des modifications soit de leur structure, soit de leur morphologie, soit de leurs propriétés. Et en plus de la variété de fonctions, chaque classe de SCNPs a le potentiel pour de nombreuses applications. Dans la première étude présentée dans cette thèse (chapitre 1), nous avons préparé une classe de SCNPs photodégradables ayant une taille ajustable et inférieure à 10 nm. Il s’agit de polyesters rendus photosensibles par la présence de coumarines à l’intérieur de la chaîne principale (nommés CAPPG) grâce à la copolymérisation de coumarine diol, d’acide adipique et de propylène glycol (PPG). Cette incorporation de coumarines dans la chaîne principale permet au polymère d’être photosensible par deux façons. En effet, les coumarines peuvent se photo-dimériser, lorsqu’elles sont irradiées par des rayonnements UV (> 320 nm) en des cyclobutanes qui peuvent être ouverts à nouveau par d’autres rayonnements UV (254 nm) permettant la restauration des coumarines initiales. Cela a permis la création de SCNPs de tailles inférieures à 10 nm et incluant des propriétés de photodégradation. Cette propriété a été démontrée par une irradiation de 3 h avec des chaînes polymères de 13220 g/mol à 1385 g/mol dans les SCNPs. La taille de ces SNCPs (caractérisée par leur rayon hydrodynamique) peut être modifiée entre 3 nm et 5,3 nm en modifiant le taux de dimérisation des coumarines, ce qui est aisément obtenu en ajustant le temps d’irradiation UV. Les résultats ont démontré que cette méthode permet un contrôle aisé de la taille des SCNPs sans avoir recours à la synthèse de nombreux polymères précurseurs. Finalement, comme le polyester était biodégradable et biocompatible, ces SCNPs peuvent être exploitées pour des applications biomédicales. Dans la deuxième étude effectuée au cours de cette thèse (chapitre 2), nous avons préparé un nouveau type de SCNPs multifonctionnel à partir d’un polymère cristallin liquide. Il s’agit du polyméthacrylate de [2- (7-méthylcoumaryl) oxyéthyle - co - 6-[4-(4’-méthoxyphenylazo) phénoxy] hexyle] (PAzoMACMA). Les groupements latéraux du polymère contiennent, en majorité, des azobenzènes photoisomérisables et, en minorité, des coumarines photodimérisables. Les azobenzènes servent de mésogènes pour la formation de cristaux liquides alors que les coumarines ont été utilisées pour une réticulation photoinduite et intrachaîne. Malgré les dimensions inférieures à 15 nm, le confinement et la réticulation, les phases cristallines liquides (LC) persistèrent même dans les SCNPs. Ces SCNPs cristaux liquides (LC-SCNPs) présentèrent un certain nombre de propriétés intéressantes et particulières. Alors que leurs dispersions dans le THF n’étaient pas fluorescentes, celles dans le chloroforme l’étaient. En plus, ces nanoparticules s’aggloméraient quelque peu dans le chloroforme ce qui induisait des fluorescences différentes entre des SCNPs riches en isomères cis ou riches en isomères trans des azobenzènes. A cause de la photoisomérisation des azobenzènes, ces LC-SCNPs se déformaient sous irradiation comme le font les microparticules ou les colloïdes contenant des azobenzènes. Cependant, la déformation de ces nanoparticules dépend de la longueur d’onde de lumière polarisée. Alors que sous irradiation UV polarisée à 365 nm, l’élongation des SCNPs était perpendiculaire à la polarisation de la lumière incidente, sous irradiation visible polarisée entre 400 et 500 nm, l’étirement se faisait parallèlement à la polarisation. Finalement, un nanocomposite fut préparé par dispersion de LC-SCNPs dans une matrice de polyméthacrylate de méthyle (PMMA). Si celui-ci était étiré mécaniquement, les azobenzènes s’orientaient dans la direction de la déformation induite. Ces propriétés intéressantes des LC-SCNPs que cette étude a permis de dévoiler, suggèrent de nouvelles applications potentielles. Dans la troisième étude de cette thèse (chapitre 3), nous avons préparé une classe de SCNPs sensibles à la présence de CO2 et leurs agrégats micellaires auto-assemblés. D’un côté, des SCNPs ont été préparées à partir d’un polyméthacrylate de {(N, N-diméthylaminoéthyle)-co-4-méthyl-[7-(méthacryloyl)-oxyéthyl-oxy] coumaryle} (PDMAEMA-co-CMA). Lorsqu’elles sont dispersées en solution aqueuse, les nanoparticules individuelles peuvent subir des cycles réversibles d’expansion et de rétrécissement sous une stimulation alternative de CO2 et de N2 qui vont protoner et déprotoner les amines tertiaires. D’un autre côté, des SCNPs de type ‘Janus’ (SCJNPs) ont été préparées à partir d’un copolymère dibloc amphiphile : PS-b-P(DMAEMA-co-CMA) (PS correspond au polystyrène qui est hydrophobe). Ce type de SCJNPs peut s’autoassembler sous forme de micelles en solution aqueuse. Sous stimulation CO2 ou N2, l’expansion ou le rétrécissement à l’intérieur des particules permet de grands changements de volume. En plus, ces particules ont été étudiées comme potentiels nanoréacteurs pour des nanoparticules d’or (AuNPs) que ce soit sous formes SCNPs ou micelles SCJNPs. La vitesse de formation des AuNPs augmente sous bullage de CO2 et décroît sous N2. Cela permet de rendre possible cette réaction contrôlable par ces deux gaz. Qui plus est, utiliser des micelles de SCJNPs dont le volume peut être modifié sur un large intervalle en changeant l’intensité de la stimulation de CO2, permit d’obtenir des AuNPs de taille variable.<br>Abstract : With interests on nanoscience and nanotechnology for many applications, there is a demand for development of fabrication technology of ultra-small nano-size objects that allow for precise size control and tailored functionality. Recently, a new technology called ‘single-chain technology’, which manipulates a single polymer chain, becomes a rapidly-growing research topic. This technology provides a facile method to prepare polymer single-chain nanoparticles (SCNPs) with a typical size of 1.5-20 nm. Due to the ultra-small size-enabled unique properties, SCNPs have wide range of applications, including sensor, catalytic system, low viscosity coating, nanoreactor and biomedical applications. Through the contributions by many scientists in the past decade, the synthetic methodologies to fabricate SCNPs have been reported using various chemistries and been getting mature. However, there are still several unsolved problems in the field of SCNPs including functions and application. Stimuli-responsive polymers, as a class of smart materials whose properties can be changed by responding to external stimuli, have been widely used in energy and biomedical applications. Since their chemical and physical properties can be changed easily and efficiently via environmental control, stimuli-responsive polymers provide a potential pathway to preparing functional SCNPs. In this thesis, we are focusing on developing functional SCNPs, especially systems with multi-functions, and expanding their applications. To achieve this target, various stimuli-responsive polymers were prepared as polymer precursors and their stimuli-responsive properties were introduced into the SCNP systems by rational design of their chemical structures. The core of this thesis is comprised of three projects which deal with three classes of SCNPs from stimuli-responsive polymers. These stimuli-responsive SCNPs perform multi-functions and undergo certain change either in structure or morphology and properties. In addition, according to their variety of functions, each class of multi-functional SCNPs has diverse potential applications. In the first study presented in the thesis (Chapter 1), we prepared a class of sub-10 nm photodegradable and size-tunable SCNPs based on photo-responsive main-chain coumarin-based polyesters Poly{[7-(hydroxypropoxy)-4-(hydroxymethyl)coumarin adipate]-co- (polypropylene glycol adipate)} (CAPPG) through copolymerization of coumarin diol, adipic acid and polypropylene glycol (PPG). By incorporating coumarin moieties into the chain backbone of a polyester, dual photo-responsive reaction, i.e. photo-dimerization (>320 nm) and photo-induced chain scission (254 nm), occur under two different wavelengths of UV irradiation, enabling the preparation of sub-10 nm SCNPs and their photo-degradation property. The photo-degradability of SCNPs is evidenced under 254 nm UV irradiation for 3 h, which molecular weight of SCNPs decreasing from 13220 g/mol to 1385 g/mol. Moreover, the size of SCNPs can be tunable from 5.3 nm to 3 nm (hydrodynamic diameter) by varying the dimerization degree of coumarin moieties, that is simply controlled by the UV irradiation time. These results demonstrate a facile method to control the size of SCNPs without the need for synthesizing different polymer precursors. Finally, due to the biocompatible and biodegradable nature of polyester as polymer precursor, the SCNPs with photo-degradability and size-tunability have the potential to be exploited for biomedical applications. In the second study realized in this thesis (Chapter 2), we prepared a new type of multi-functional SCNPs from a side-chain liquid crystalline polymer (SCLCP), namely poly{6-[4-(4-methoxyphenylazo) phenoxy]hexylmethacrylate-co-4-methyl-[7-(methacr-yloyl) oxy-ethyl-oxy]coumarin} (PAzoMACMA). The polymer’s side groups comprise photo-isomerizable azobenzene in majority and photo-dimerizable coumarin in minority, with the former as mesogens and the latter for intra-chain photo-crosslinking. Despite the sub-15 nm size, confinement and crosslinking, the liquid crystalline (LC) phases of bulk PAzoMACMA persist in SCLCPs. Such LC-SCNPs exhibit a number of interesting and peculiar properties. While their dispersion in THF is non-fluorescent, when dispersed in chloroform, the nanoparticles appear to agglomerate to certain degree and display significant fluorescence that is different for SCNPs rich in the trans or cis isomer of azobenzene. The azobenzene LC-SCNPs also undergo photo-induced deformation, similar to azobenzene micro- or colloidal particles. However, the elongational deformation of the nanoparticles is dependent upon the linearly polarized excitation wavelength. While under polarized 365 nm UV irradiation the SCNP stretching direction is perpendicular to the light polarization, under polarized 400-500 nm visible light irradiation, the stretching takes place along the light polarization direction. Finally, an all-polymer nanocomposite was prepared by dispersing the LC-SCNPs in poly(methyl methacrylate) (PMMA), and mechanically stretching-induced orientation of azobenzene mesogens developed along the strain direction. The interesting properties of LC-SCNPs unveiled in this study suggest new possibilities for applications including bio-imaging and LC materials. As the third study in this thesis (Chapter 3), we studied a class of CO2-responsive SCNPs and their self-assembled micellar aggregates. On one hand, SCNPs are prepared from a random copolymer of poly{(N,N-dimethylaminoethyl methacrylate)-co-4-methyl-[7-(methacryloyl)oxyethyl-oxy]coumarin} (P(DMAEMA-co-CMA)). When dispersed in aqueous solution, individual nanoparticles can undergo reversible swelling/shrinking under alternating CO2/N2 stimulation as a result of the reversible protonation/deprotonation of tertiary amine groups. On the other hand, tadpole-like single-chain ‘Janus’ nanoparticles (SCJNPs) are prepared using an amphiphilic diblock copolymer of PS-b-P(DMAEMA-co-CMA) (PS is hydrophobic polystyrene). This type of SCJNPs can self-assemble into core-shell micellar aggregates in aqueous solution. Under CO2/N2 stimulation, the collective swelling/shrinking of SCJNPs within the micelle results in large, reversible volume change. In addition, both P(DMAEMA-co-CMA) SCNPs and PS-b-P(DMAEMA-co-CMA) SCJNP micelles are explored as gas-tunable nanoreactors for gold nanoparticles (AuNPs). The rate of AuNP formation increases under CO2 stimulation and decreases upon N2 bubbling, which makes it possible to tune the reaction rate up and down (on/off switching) by using the two gases. Moreover, using the micelles of SCJNPs, whose volume can be controlled over a wide range by adjusting the CO2 stimulation strength, variable-size AuNPs and their aggregates are obtained with continuous redshift of the surface plasmon resonance (SPR) into the long wavelength visible light region.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>The short-wave infrared region (SWIR; 1000-2000 nm) has excellent properties for in vivo imaging: low autofluorescence, reduced scattering, and little light absorption by blood and tissue. However, broad adoption of SWIR imaging in biomedical research is hampered by the availability of versatile and bright contrast materials. Quantum dots (QDs) are bright, compact SWIR emitters with narrow size distributions and emission spectra, qualities that make them ideal for labeling and multiplex SWIR imaging. Nevertheless, SWIR QDs have limited applications due to the shortcomings of established ligand systems. Established ligands result in QD probes with limited colloidal stability, large size and broad size distribution, or all three limitations. To address these limitations, we turned to polymeric ligands, beginning with the polymeric imidazole ligand (PIL) initially developed for visible-emitting CdSe/CdxZn₁₋xS QDs with L-type native ligands. We studied ligand exchange with PIL and InAs/CdSe/CdS SWIR QDs with native X-type ligands in a variety of conditions but only saw limited exchange. Our results combined with reports in the literature suggest that the mechanism of X-to-L ligand exchange is not amenable to polymeric ligands. These results led us to the concept of ligand-type matching: for straightforward exchange, QD native ligands should be the same type as the binding groups on the polymer. Thus, we synthesized InAs/CdSe/ZnS with L-type native ligands, which exchanged readily with PIL to produce probes with (<14 nm hydrodynamic diameter, Hd). We also synthesized a new ligand that is compatible with oleate-capped QDs: the polymeric acid ligand (PAL), which features carboxylic acids as the binding group and PEG₁₁ chains to solubilize the QD-ligand construct. We exchanged PAL with oleate-capped PbS and PbS/CdS QDs, resulting in compact probes ( <11 nm Hd) with narrow size distribution. The small size and narrow size distribution of these constructs are preserved for several months when stored in isotonic saline solution in air, addressing the size and stability limitations of existing ligand systems for SWIR QDs. Our constructs are bright in vivo and to demonstrate their suitability for imaging, we performed whole-body imaging as well as lymphatic imaging, including visualization of lymphatic flow.<br>by Daniel Mauricio Montana Fernandez.<br>Ph. D.

2012 - 2013<br>This PhD project is focused on the development of new polymeric materials with antibacterial and antifungal activity. The first part of the work was dedicated to the synthesis and the insertion of a modified amino acid into an antimicrobial peptide (AMP), with the aim to retain the action mechanism on bacterial membranes. Understanding the mechanism of action of AMPs is important for the rational design of new drugs. For this reason, I have collected structural properties, antimicrobial activity values and biological origin of antimicrobial peptides from published data. I have calculated the most relevant chemical physical properties like charge, hydrophobic moment, helicity, flexibility, isoelectric point, Boman and instability index and penetration capabilities. This data collection work permitted us to create YADAMP (www.yadamp.unisa.it), a web database with detailed informations on AMPs. YADAMP database contains the highest number of active sequences with proven antimicrobial activity. YADAMP peremitted me to do a work of data mining that end up with the choice of a peptide, a defensine, to be used as template for developing a new photoresponsive peptide. The peptide, hereafter indicated as ALY, is a short α-helix, membrane active AMP with a tyrosine in the sequence. I have developed the modified analogue replacing the tyrosine by a modified tyrosine with azobenzene group in the side chain. The modified amino acid, named Fmoc-azoTyr, was synthesized according to the classic scheme of diazocopulation reactions. I have chosen the azobenzene group because it permits a reversible trans to cis photochemical isomerization... [edited by author]<br>XII n.s.

Impact resistant materials (IRMs) are widely used in the automotive and packaging industry. Their main purpose is the protection of the transported occupants or goods. Cellular materials as well as structures combine lightness with large deformation under load. The energy absorption mechanism is provided by limiting the peak load and ensuring the elastic deformation of the IRMs. Polymeric foams are largely used as IRMs due to their cellular structure. Prediction of the foam properties in terms of Young’s Modulus (Elastic Modulus) and the onset of Plateau Region can be related to the foam density and the mechanical properties of the bulk material (Gibson and Ashby model). The structure of the foam is only partly accounted for in the Gibson and Ashby model in terms of material density. However, it is possible to produce cellular materials with the same density but very different internal architectures. This cannot easily be exploited in conventional polymer foams but the processing of High Internal Phase Emulsion (PolyHIPE) and its polymerisation route to produce PolyHIPE Polymers (PHPs) can produce materials with very different structures. Experiments have revealed that the PHPs properties are dictated by their detailed structure. Elastic PHPs with: 1) varying ratio of polymerizable oil phase with respect to aqueous phase and 2) varying mixing time/energy input were produced and tested by mechanical compression at different temperatures and strain rates. The elastic modulus increases with a quadratic law as a function of the polymerizable oil phase content of the HIPE when the mixing time is the same, as predicted by the model. The Specific Absorption Energy (SAE), represented by the area under the stress-strain curve, increases in a similar way. Increasing mixing time on HIPE has the effect of modifying the cellular structure. Smaller pores and narrower distribution of pores are observed. Such features are consistent for any set of PHPs densities and represent a design tool when some specific mechanical characteristics are prescribed. The assessment of process-structure-properties relationships was performed by combining the mechanical response of the various PHPs with the imaging of their structure by Scanning Electron Microscopy. The properties of PHPs were benchmarked with reference to two commercially available products. One material is characterised by a porous structure with a relatively high Young’s Modulus while the other by a non-porous and composite-like solid structure with lower elastic modulus. The properties of the PHPs can be engineered to shift from a foam-like material to a composite-like through the processing parameters which in turn modify the material porous structure. The temperature has very limited effect on the PHPs material unlike for the reference commercial materials. The enhancement of properties (increasing Elastic Modulus and SAE) induced by changing the processing route are remarkable for such a class of porous materials. When plotted on a Modulus-Density chart, the PHPs fill an existing material-chart gap, representing a new class of materials and opening new possibilities as IRMs.

Titanium dental implants are a commonly used solution for the replacement of lost teeth. Even though the success rate is high, the number of infections related to the placement of the implant is still remarkable and may impair the proper function of the device, leading to health and economic costs. The infections related to medical devices start with a bacterial adhesion and proliferation on the material surface, leading to the formation of a complex biofilm able to protect the bacteria from the host immune response and the treatment with antibiotic. Due to the difficulty of treatment of the implant site one the biofilm is settled, one of the strategies to avoid the infection is to deal with the initial bacterial adhesion. This PhD thesis deals with the development of polymeric antibacterial coatings on titanium for dental implants, focusing on the achievement of fast and cost-effective procedure. With this aim, different coating strategies have been developed, tested and compared. A pre-treatment of the titanium surface was optimized in the first part of the thesis in order to achieve a clean surface and to enhance the chemical reactivity of the titanium oxide. With this aim, low pressure plasma activation was the selected method. The use of plasma activation allows for the removal of organic contaminants while increasing the surface energy of the treated surfaces. For the preparation of the polymeric antibacterial coatings, two different antifouling polymers have been used, namely, polyethylene glycol (PEG) and poly-2-hydroxyethylmetacrylate (PHEMA). PEG coatings were prepared by three different techniques, a wet chemical technique (silanization), a plasma enhanced chemical vapor deposition and an electrochemical process (electrodeposition). The three methods rendered an ultra-thin coating able to resist the bacterial adhesion. On the other hand, PHEMA-like coatings were prepared in a novel set-up by treating the liquid monomer by a plasma jet. Moreover, the different coatings were biofunctionalized in order to achieve multifunctionality and enhance the performance of the coating. For instance, the combination of PEG with a cell adhesion peptide (RGD) reported a better human fibroblast adhesion while maintaining the antifouling properties of the coating. PEG was also used as a platform for the immobilization of antimicrobial peptides (AMP). The bonding of the polymer with the AMP was optimized, achieving a surface able to reduce the bacterial adhesion and to kill the bacteria still able to adhere to the surface. Finally, the combination of two different plasma polymerized coatings with antibiotics (either Doxycycline or Vancomycin) was used as a drug delivery system.<br>Els implants dentals de titani són la solució més estesa per substituir peces dentals. Tot i que les taxes d'èxit són elevades, el nombre d'infeccions relacionades amb la col·locació de l'implant és elevat, i influeix en el mal funcionament de l'implant, amb un elevat cost tan a nivell econòmic com de salut. Les infeccions associades als dispositius sanitaris comencen amb una adhesió i proliferació dels bacteris a la superfície del material, que comporta la formació d'un biofilm capaç de protegir els bacteris de l'acció del sistema immunitari de l'hoste i del tractament amb antibiòtics. Aquesta tesi doctoral es basa en el desenvolupament de recobriments polimèrics antibacterians en titani per aplicacions dentals, buscant aconseguir mètodes ràpids i econòmics. Per tal d'assolir aquest objectiu, s'han desenvolupat, provat i comparat diferents estratègies per obtenir els recobriments. En la primera part de la tesi s'ha optimitzat un pretractament de la superfície del titani, per tal d'obtenir una superfície neta i millorar la reactivitat química de l'òxid de titani. El mètode seleccionat per l'activació ha estat l'activació per plasma, que permet eliminar els contaminants orgànics i augmentar l'energia superficial de les mostres tractades. Els polímers seleccionats per als recobriments han estat el polietilenglicol (PEG) i el 2-hidroxietilmetacrilat (PHEMA), que tenen propietats antifouling. Per preparar els recobriments de PEG s'han utilitzat tres mètodes diferents, la silanització, la polimerització per plasma i l'electrodeposició. Els tres mètodes han donat com a resultat una capa fina capaç de resistir l'adhesió bacteriana. Per altra banda, els recobriments amb PHEMA s'han preparat amb una nova metodologia, tractant el líquid amb un plasma jet. Els diversos recobriments s'han biofuncionalitzat per tal d'aconseguir una multifuncionalitat i millorar el seu funcionament. La combinació del PEG amb un pèptid d'adhesió cel·lular ha permès millorar l'adhesió de fibroblasts i mantenir les propietats antifouling del recobriment. La immobilització de pèptids antibacterians al PEG permet obtenir una superfície resistent a l'adhesió bacteriana i amb efecte antibacterià sobre els bacteris capaços d'adherir-se al recobriment. Per últim, la combinació de dos recobriments preparats per polimerització per plasma amb dos antibiòtics (vancomicina o doxiciclina) permet obtenir un sistema d'alliberació de fàrmacs a la superfície del titani.

Poly(lactic acid) possesses many desirable properties, above all biodegradability an compostability. PLA can be either amorphous or semicrystalline depending on its stereochemistry and thermal history. A high crystallinity degree is desirable to increase the heat resistance of PLA but it is rather difficult to reach high values during injection and compression moulding due to its very slow crystallization kinetics. Therefore, two different approaches can be carried out. The first concerns the synthesis and use of a PLA stereocomplex by mixing PLLA and PDLA, because this blend has shown higher crystallization rates and higher melting temperature than the single homopolymers. The second approach regards the adding of a nucleating agent that favours the formation of the PLA spherulites. In my thesis project, funded by SACMI Imola, an innovative process for the processing of PLA by compression moulding was developed. The study was focused on two different aspects. The first regarded the formation and crystallization of the stereocomplex by means a Rheo-Raman instrument. The second aspect regarded the investigation of some operative parameters for the compression moulding process for the production of coffee-pods. The results regarding the stereocomplex have shown that its formation is strongly affected from two different parameters that are the temperature of the experiment and the shear rate applied. By means the Rheo-Raman analysis it was also possible to monitor on line the formation and crystallization of the stereocomplex, that takes place in relatively short time (1-2 minutes). As far as the processing of PLA by means compression moulding is concerned, the attention was focused on the thermal treatments after the formation of the coffee pod. This thermal treatment, carried out by means a post-mould device, favours the post crystallization process of the polymer leading to reach the target value requested for the application in the coffee machines.

[ES] En la presente tesis doctoral se ha evaluado el uso de nuevos soportes celulósicos y silíceos como sistemas de filtración para la estabilización y conservación de alimentos líquidos con el fin de afrontar dos grandes retos de la industria de bebidas. Por un lado, evitar o minimizar los cambios en las propiedades nutricionales, estructurales y organolépticas de los alimentos, ocasionados por la pasteurización térmica tradicional, y ofrecer una alternativa al problema de la baja viabilidad debida a los altos costos de inversión/producción al aplicar nuevas tecnologías no térmicas. Por ello, esta tesis doctoral se centra en el desarrollo y evaluación de una nueva tecnología no térmica de conservación de alimentos líquidos basada en la filtración. Se han desarrollado sistemas de filtración a partir de soportes celulósicos y silíceos, sin funcionalizar o funcionalizados con compuestos antimicrobianos. En el primer capítulo se evaluó el uso de materiales de celulosa como soportes filtrantes para el tratamiento de alimentos líquidos. Como primera aproximación se desarrolló un material poroso nano-micro tubular a partir de la extracción y deslignificación del material celulósico presente en el corazón o raquis de la mazorca de maíz. El uso de este soporte resultó ser efectivo como material filtrante para el tratamiento de agua y zumo de naranja, en un sistema de flujo continuo, eliminando la carga microbiana. La aplicación de este soporte como sistema de filtración presenta diversas ventajas como su capacidad de retención microbiana, la reutilización de sub-productos del maíz y, por tanto, su respeto al medioambiente. Sin embargo, sería necesario optimizar el proceso de filtrado para evitar la frecuente obturación de sus poros que requirió varios ciclos de lavado durante el proceso, así como establecer un método de regeneración del material para incrementar su vida útil. Además, este sistema afectó al color del zumo filtrado, que no se mantuvo constante durante el proceso, lo que supone una importante desventaja que es necesaria abordar. Como segunda aproximación, se evaluó el potencial de la inmovilización de una molécula bioactiva sobre membranas de celulosa, para mejorar la capacidad de retención microbiana del material celulósico, así como permitir su reutilización. Los filtros de celulosa funcionalizados con poliaminas demostraron ser eficaces en la eliminación de patógenos en agua, debido a las cargas positivas generadas por los grupos amina inmovilizados en la superficie de las membranas, que atraen y retienen las bacterias cargadas negativamente. Dada la fácil preparación y procedimiento de uso de las membranas de celulosa funcionalizadas con poliaminas, éstas podrían ser consideradas una buena opción para el desarrollo de sistemas de tratamiento de aguas in situ, rápidos, de fácil manejo y de bajo coste. El segundo capítulo describe el desarrollo y aplicación de partículas de sílice funcionalizadas con compuestos de aceites esenciales, con el fin de diseñar coadyuvantes de filtración con actividad antimicrobiana. La filtración de diversas matrices alimentarias (agua, cerveza y zumo de manzana) a través de los soportes funcionalizados con los antimicrobianos naturales demostró ser eficaz en la reducción del recuento de la cepa patógena Escherichia coli, así como frente a la microflora endógena de la cerveza y el zumo (bacterias acidolácticas, aerobios mesófilos, psicrófilos, mohos y levaduras). La eficacia en el control microbiano se debe a la combinación de la adsorción física y la inactivación por contacto con los compuestos de aceites esenciales inmovilizados. Además, la evaluación de las propiedades físico-químicas y sensoriales de los alimentos líquidos demostró un efecto poco significativo, éste depende del tamaño de las partículas de sílice usadas y de la molécula bioactiva inmovilizada. Por lo tanto, el sistema de conservaci�<br>[CAT] En la present tesi doctoral s'ha avaluat l'ús de nous suports cel·lulòsics i silicis com a sistemes de filtració per a l'estabilització i conservació d'aliments líquids, amb la finalitat d'afrontar dos grans reptes de la indústria de begudes. D'una banda, evitar o minimitzar els canvis en les propietats nutricionals, estructurals i organolèptiques dels aliments, ocasionats per la pasteurització tèrmica tradicional, i oferir una alternativa al problema de la baixa viabilitat deguda als alts costos d'inversió/producció en aplicar noves tecnologies no tèrmiques. Per això, aquesta tesi doctoral es centra en el desenvolupament i avaluació d'una nova tecnologia no tèrmica de conservació d'aliments líquids basada en la filtració. S'han desenvolupat sistemes de filtració a partir de suports cel·lulòsics i silicis, sense funcionalitzar o funcionalitzats amb compostos antimicrobians. En el primer capítol es va avaluar l'ús de materials de cel·lulosa com a suports filtrants per al tractament d'aliments líquids. Com a primera aproximació es va desenvolupar un material porós nano-micro tubular a partir de l'extracció i deslignificació del material cel·lulòsic present en el cor o raquis de la panolla de dacsa. L'ús d'aquest suport va resultar ser efectiu com a material filtrant per al tractament d'aigua i suc de taronja, en un sistema de flux continu, eliminant la càrrega microbiana. L'aplicació d'aquest suport com a sistema de filtració presenta diversos avantatges com la seua capacitat de retenció microbiana, la reutilització de subproductes de la dacsa i, per tant, el seu respecte al medi ambient. No obstant això, seria necessari optimitzar el procés de filtrat per a evitar la freqüent obturació dels seus porus que va requerir diversos cicles de rentada durant el procés, així com establir un mètode de regeneració del material per a incrementar la seua vida útil. A més, aquest sistema va afectar el color del suc filtrat, que no es va mantenir constant durant el procés, la qual cosa suposa un important desavantatge que és necessari abordar. Com a segona aproximació, es va avaluar el potencial de la immobilització d'una molècula bioactiva sobre membranes de cel·lulosa, per a millorar la capacitat de retenció microbiana del material cel·lulòsic, així com permetre la seua reutilització. Els filtres de cel·lulosa funcionalitzats amb poliamines van demostrar ser eficaces en l'eliminació de patògens en aigua, a causa de les càrregues positives generades pels grups amina immobilitzats en la superfície de les membranes, que atrauen i retenen els bacteris carregats negativament. Donada la fàcil preparació i procediment d'ús de les membranes de cel·lulosa funcionalitzades amb poliamines, aquestes podrien ser considerades una bona opció per al desenvolupament de sistemes de tractament d'aigües in situ, ràpids, de fàcil maneig i de baix cost. El segon capítol descriu el desenvolupament i aplicació de partícules de sílice funcionalitzades amb compostos d'olis essencials, amb la finalitat de dissenyar coadjuvants de filtració amb activitat antimicrobiana. La filtració de diverses matrius alimentàries (aigua, cervesa i suc de poma) a través dels suports funcionalitzats amb els antimicrobians naturals va demostrar ser eficaç en la reducció del recompte del cep patogen Escherichia coli, així com enfront de la microflora endògena de la cervesa i el suc (bacteris àcid làctics, aerobis mesòfils, psicròfils, floridures i llevats). L'eficàcia en el control microbià es deu a la combinació de l'adsorció física i la inactivació per contacte amb els compostos d'olis essencials immobilitzats. A més, l'avaluació de les propietats fisicoquímiques i sensorials dels aliments líquids estudiats va demostrar un efecte poc significatiu, aquest depèn de la grandària de les partícules de sílice usades i de la molècula bioactiva immobilitzada. Per tant, el sistema de conserv<br>[EN] In the present doctoral thesis the use of new cellulosic and silica supports as filtering systems for the stabilization and preservation of liquid foods has been evaluated to overcome two major challenges of the beverage industry. On the one hand, avoid or minimize the changes in the nutritional, structural and organoleptic properties of food caused by traditional thermal pasteurization, and offer an alternative to the problem of low viability due to high investment/production costs when applying new non-thermal technologies. Therefore, this doctoral thesis focuses on the development and evaluation of a new non-thermal technology for the preservation of liquid foods based on filtration. The filtering systems have been developed from cellulosic and silica supports, non-modified or functionalized with antimicrobial compounds. In the first chapter, the use of cellulose materials as filtering supports for the treatment of liquid foods was evaluated. As first approximation, a porous nano-micro tubular material was developed from the extraction and delignification of the cellulosic material present in the corn stalk. The use of this support was effective as filtering material for the treatment of water and orange juice, in a continuous flow system, eliminating the microbial load. The application of this support as filtering system has several advantages, such as its microbial retention capacity, the reuse of corn by-products and, therefore, its respect for the environment. However, it would be necessary to optimize the filtering process to avoid the frequent clogging of its pores that required several washing cycles during the process, as well as to establish a method of material regeneration to increase its life. In addition, this system affected the color of the filtered juice, which did not remain constant during the process, representing an important disadvantage that must be addressed. As a second approach, the potential of the immobilization of a bioactive molecule on cellulose membranes was evaluated to improve the microbial retention capacity of the cellulosic material, as well as to allow its reuse. The cellulose filters functionalized with polyamines proved to be effective in eliminating pathogens in water, due to the positive charges generated by the amine groups immobilized on the surface of the membranes, which attract and retain the negatively charged bacteria. Given the easy preparation and usage of the polyamines-functionalized cellulose membranes, these could be considered a good option for the development of fast, easy to use and low cost in situ water treatment systems. The second chapter describes the development and application of silica particles functionalized with essential oil components to design filtering aids with antimicrobial activity. The filtration of various food matrices (water, beer and apple juice) through the supports functionalized with natural antimicrobials proved to be effective in reducing the load of the pathogenic strain Escherichia coli, as well as reducing the endogenous microflora of beer and the juice (lactic acid bacteria, mesophilic, psychrophilic, mold and yeast). The removal capability is due to the combination of physical adsorption and contact inactivation with the essential oil compounds immobilized. In addition, the evaluation of the physicochemical and sensory properties of the liquid foods studied showed a not significant effect, it depends on the size of the silica particles used and the immobilized bioactive molecule. Therefore, the proposed preservation system has a high potential for cold beverage pasteurization processes.<br>N. Peña-Gomez would like to thank for financial support in the frame of her PhD project to Operational Programme of the European Social Fund (ESF) 2014-2020, the Agencia Estatal de Investigación, Generalitat Valenciana and FEDER-EU (Projects RTI2018-101599-B-C21 and AGL2015-70235-C2-1-R). The authors also thank the Electronic Microscopy & Microanalysis Laboratory at Patras University for support.<br>Peña Gomez, N. (2020). Development of polymeric and silica filtering materials functionalized with antimicrobial compounds for the elimination of microorganisms in liquid food [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/137041<br>TESIS

In the construction industry, prepainted metal strip is a widely used material for fagade and roofs of building intended for commercial used. The physical properties of modem coatings are outstanding, however one big problem that remains and which affects the overall coatings performance is dirt pick up. Firstly the effect of weathering induced chemical composition change was evaluated using photo-acoustic infrared spectroscopy (PA-FTIR), and X-ray photoelectron spectroscopy (XPS). The results shown that photo-oxidation processes occurs via Norrish type I and type 11 reaction at several sites on the polymer backbone, with the ester linkage and the melamine crosslinkage being the more reactive. Secondly aluminosilicates have been found to be the main source of soiling with organic pollutants also responsible but to a minor extent, the presence of such dirt was confirmed by XPS analyses. Unusual peak shape was observed on the carbon narrow scans with low binding photoelectron emitted. Finally Polymer/organically modified layered silicates (PLS) nanocomposites are a new class of filled polymer with ultrafine phase dimension. They improve considerably the physical properties of the coating while reducing dirt pick up. The best results were obtained when the insitu intercalative method was used. However the implication of the onium salts is obscure and the relation between the nanocomposite structure and its properties is not well understood.

<p> Rural communities in developing countries are most vulnerable to the plight of requiring repeated infusions of charitable aid over time. Micro-business opportunities that effectively break the cycle of poverty in resource-rich countries in the developing world are limited. However, a strong model for global commerce can break the cycle of donor-based economic supplements and limited local economic growth. Sustainable economic development can materialize when a robust framework combines engineering with the generous investment of profits back into the community. This research presents a novel, systems-based approach to sustainable community development in which a waste-to-resource methodology catalyzes the disruption of rural poverty. </p><p> The framework developed in this thesis was applied to the rural communities of Cagmanaba and Badian, Philippines. An initial assessment of these communities showed that community members are extremely poor, but they possess an abundant natural resource: coconuts. The various parts of the coconut offer excellent potential value in global commerce. Today the sale of coconut water is on the rise, and coconut oil is an established $3 billion market annually that is also growing rapidly. </p><p> Since these current industries harvest only two parts of the coconut (meat and water), the 50 billion coconuts that grow annually leave behind approximately 100 billion pounds of coconut shell and husk as agricultural waste. Coconuts thus provide an opportunity to create and test a waste-to-resource model. Intensive materials analysis, research, development, and optimization proved that coconut shell, currently burned as a fuel or discarded as agricultural waste, can be manufactured into high-grade coconut shell powder (CSP), which can be a viable filler in polymeric composites. </p><p> This framework was modeled and tested as a case study in a manufacturing facility known as a Community Transformation Plant (CTP) in Cagmanaba, Philippines. The CTP enables local creation of globally viable products from agricultural waste. This researcher seeks to encourage the propagation of CTPs throughout developing communities worldwide, each profiting from its own waste-to-resource value.</p>

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.<br>Hybrid polymeric composites (HPC) are widely used for the design of aerospace, automobile and civil engineering structures. One of the major challenges posed by these materials and structures is their brittle nature. When subjected to impact and dynamic loads, the polymeric composite structures undergo micro cracking. The cracks coalesce, propagate and can lead to catastrophic failure of the material and structures. In this thesis, an intelligent hybrid polymeric composite (IHPC) beam with healing ability was developed and tested. The IHPC beam developed consisted of a 3% prestrained 1mm diameter Ni-Ti shape memory alloy (SMA) wire actuator embedded in the polymeric host matrix. The function of the embedded Ni-Ti shape memory alloy was to enhance intelligence and healing ability to the IHPC beam. Upon electric current resistance heating, the Ni-Ti SMA actuator responds by contracting as a result of detwinned martensite → austenite phase transformation. Contraction of the SMA in the IHPC beam was utilized to stiffen and enhance healing by retarding crack growth and recovery of the strain induced in the loaded IHPC beam. This can result to increase of the flexural stiffness EI (defined as the product of the Young’s Modulus E of the material and the moment of inertia I of the geometry of the beam) and mode I fracture stress intensity factor KIC of the IHPC beam. One (1) mm diameter Ni-Ti SMA wire was used in the experimental work in this thesis. The wire was cut into 35 pieces, 200 mm long each. Ni-Ti SMA wires were heated in the furnace to a temperature of 250ºC for ten (10) hours then were left to cool in the ambient air. The heat treatment was aimed to release any residual stress and to stabilize the austenite start (AS) and austenite finish (Af) transformation temperatures of the Ni-Ti SMA. After heat treatment, the Ni-Ti SMA wires were prestrained by 3% (based on a gauge length of 150mm) on a tensile testing machine. Prestraining of the Ni-Ti SMA wires was aimed to induce detwinned martensite volume fraction in them hence increasing the transformation strain and recovery force of the Ni-Ti SMA actuator. Intelligent hybrid polymeric composite (IHPC) beams and polymeric virgin (PV) beams, all of dimensions 150mmx25mmx10mm were manufactured by casting 60D polyurethane thermosetting epoxy resin in a silicon mould. transformation strain and recovery force of the Ni-Ti SMA actuator.

Metallic robotic arms, or manipulators, currently dominate automated industrial operations, but due to their intrinsic weight, have limited usefulness for large-scale applications in terms of precision, speed, and repeatability. This thesis focuses on exploring the feasibility of using polymeric composite materials for the construction of long-reach robotic arms. Different manipulator layouts were investigated and an ideal design was selected for a robotic arm that has a 5 [m] reach, 50 [kg] payload, and is intended to operate on large objects with complex curvature. The cross-sectional geometry of the links of the arm were analyzed for optimal stiffness- and strength-to-weight ratios that are capable of preserving high precision and repeatability under time-dependent external excitations. The results lead to a novel multi-segment link design and method of production. A proof-of-concept prototype of a two degrees-of-freedom (2-DOF) robotic arm with a reach of 1.75 [m] was developed. Both static and repeatability testing were performed for verification. The results indicated that the prototype robot main-arm constructed of carbon fiber-epoxy composite material provides good stiffness-to-weight and strength-to-weight ratios. Finite element analysis (FEA) was performed on a 3-D computer model of the arm. Successful verification led to the use of the 3-D model to define the dimensions of an industrial-sized robotic arm. The results obtained indicate high stiffness and minimal deflection while achieving a significant weight reduction when compared to commercial arms of the same size and capability.

Cellulose nanofibrils are a biobased and renewable material with potential to be used in many different applications. Such applications include air filtration, absorption of liquids, and thermal insulation.  To be used for these applications the cellulose nanofibrils must form a porous and dry material. However, maintaining some degree of porosity after drying is difficult, since the fibrils are extracted in liquid and tend to collapse into a dense material upon drying. Certain methods have proven effective for making a dry porous material from cellulose nanofibrils, but these are often expensive and not suitable for large scale production. The aim of this project is to test possible methods for making a highly porous cellulose nanofibril-based material. These methods must be environmentally sustainable and suitable for large scale production. An extensive screening has been conducted with the aim of identifying methods resulting in materials with high porosity. The obtained materials have been analysed further to give a more thorough understanding of the porosity as well as other characteristics. The results indicate that cross-links in the material strengthen the structure, and that drying samples from water always results in complete collapse or very dense materials while drying samples from certain solvents other than water results in more porous materials. The analysed materials had very different porosities, some of which were relatively high. The most porous material analysed by Brunauer-Emmett-Teller gas adsorption had a surface area of 9.5 m2/g. This project gives insight into how cross-linking chemistries and treatment with different solvents and pH affect the resulting cellulose nanofibril-based material, as well as knowledge about which methods can be used to successfully produce dry porous cellulose nanofibril-based materials.

The use of redox activity as a switch in the design of multifunctional systems – materials that are capable of changing their properties as a function of the redox state – has received limited attention in the literature despite the high versatility and potential this strategy poses. The well-known redox and spectral properties of triarylamines make them ideal redox-active moieties for incorporation into multifunctional materials. This thesis investigates the design, synthesis and application of triarylamine redox-active multifunctional materials. Materials ranging from discrete complexes to crystalline coordination polymers and amorphous organic polymers were explored. From a fundamental perspective, a series of discrete Ru2+, Rh3+, Ir3+ and Re+ molecular complexes containing novel bispyrazolylmethane ligands with the triarylamine core were synthesised and their spectral and electronic properties investigated. Higher dimensionality materials, Metal-Organic Frameworks (MOFs) and Porous Organic Polymers (POPs) containing triarylamines were then explored, where the spectral, fluorescence and host-guest properties of the materials were able to be tuned as a function of the redox state. In situ UV/Vis/NIR, EPR and fluorescence spectroelectrochemical techniques in both the solution and solid-states formed an integral part of the characterisation of these advanced materials. The work in this thesis describes a systematic approach towards the study of the fundamental and applied aspects of redox activity as a platform for multifunctional systems. This study should pave the way towards the design of redox active multifunctional materials with increasing functionality that can be controlled and fine-tuned.

A úlcera de pressão é um ferimento que acomete grande número de pessoas hospitalizadas, incapacitadas de movimentação e os idosos. As alterações fisiológicas do envelhecimento seja no sistema cardiocirculatório, respiratório, renal ou no próprio sistema nervoso central, são as responsáveis pela maior predisposição dos idosos a complicações durante a hospitalização. A idade avançada é um dos fatores importantes no desenvolvimento da úlcera de pressão, pois ocorrem muitas mudanças, como o achatamento da junção entre a derme e a epiderme, menor troca de nutrientes, menor resistência à força de cisalhamento, diminuição da capacidade de redistribuir a carga mecânica da pressão. A úlcera de pressão pode ser definida como uma área localizada de necrose celular que tende a se desenvolver quando o tecido mole é comprimido entre uma proeminência óssea e uma superfície dura por um período prolongado de tempo. O tratamento para esse problema é difícil devido ao custo, ao tempo necessário para a cicatrização, aos constantes cuidados e deve proteger a ferida, ser biocompatível e fornecer uma hidratação ideal. Os biomaterias, entre eles, a quitosana apresenta características próprias para um curativo numa lesão grave. O objetivo desse trabalho foi preparar um curativo à base de quitosana que apresente propriedades adequadas ao tratamento de ferimentos relacionados à lesão de pele. O curativo foi obtido a partir da solução de quitosana, um polímero proveniente da quitina, que é encontrada principalmente em cascas de camarões, lagostas e insetos, sendo seco em estufa ou liofilizado, com ou sem suporte mecânico, em diferentes concentrações (1,2,3 e 6%), e em associação com outras substâncias. As membranas com melhores características mecânicas foram aquelas secas por liofilização, com suporte mecânico. Dessas, a que teve uma maior absorção de solução fisiológica 0,9% foi a membrana de quitosana a 1%, liofilizada com poliéster, que apresentou também, a melhor característica física sensorial e melhor preço. A fotomicrografia mostrou que as membranas com maior retenção de líquido apresentaram os maiores poros. Foi obtido, assim, curativos com as qualidades propostas no presente trabalho.<br>The pressure ulcer is a wound that commits a great number of hospitalized people, people disabled of movement and the elders. The main important factorsthat contribute to the elder\'s predisposition to clinical complications are physiological alterations in the aging process involving the cardiovascular system, respiratory, renal ou even in the central nervous system. The advanced age is one of the important factors in the development of the pressure ulcer therefore many changes may occur such as dermis and epidermis junction f1attening, nutrients decrease exchange, shear force decrease resistance and reduction of the capacity to redistribute the pressure mechanical load. The pressure ulcer may be defined as a cellular necrosis area that tends to develop when the soft skin tissue is compressed over a bony proeminence over a long period of time. The main reasons the treatment is so difficult are as follows: time necessary for scarifying process, constant care and wound protection, must be biocompatible and must provide ideal moisturizing. Biomaterials such as chitosan, presents optimal characteristics for a curative in acute lesions. In this present work the objective was the development of a chitosan made of curative that had adequate properties for treatmente of skin lesion related wounds. The curative was obtained from a chitosan solution which is a polymer obtained from chitin (which is commonly found in shrimp, lobsters and insect shells) and can be both heat-dried or lyophilized, with ou without mechanical support structure, in different solutions concentrations (1, 2, 3 and 6%) and also in association with other substances. The membranes with the best mechanical characteristics where those dried by lyophilization and with mechanical support structure. In this group the one that had the best physiological solution 0,9% absorption was the chitosan 1% lyophilized with polyester that also presented the best physical-sensorial characteristics and best price. The photomicrography showed that membranes with greater liquid retention presented the best pore size. This way, curatives where then obtained with the qualities proposed by this presente work.

This thesis has dealt with the preparation and the characterization of piezoelectric 0-3 composite materials. The technological aim is to evaluate a material potentially suitable for the development of a sensitive skin for human robotics. As secondary objectives this material should be cheap (relatively) and easy processable in order to make it possibly adaptable for industrial production. For these reasons, 0-3 composites were prepared and characterized. Raw materials were selected among the most commonly used for piezoelectric applications. PVDF is the most widely used ferroelectric polymer. It was used along with two of its copolymers: PVDF-HeFP, developed to have improved flexibility but no piezoelectricity and PVDF-TrFE, developed to obtain the crystalline piezoelectric phase whatever the process. PMMA was also studied. Barium titanate submicron-powder was chosen as piezo-active filler. Composites were prepared with increasing volume percentages of fillers. Two different processing methods were explored in order to evaluate their effect on the microstructure and the piezoelectric response

Laser Sintering is an Additive Manufacturing technology that uses digital files to construct 3-dimensional parts by depositing and consolidating layers of powdered material. Application of the technology for metal and ceramic powders is common but the focus of this work was on polymer laser sintering. A significant drawback for polymer laser sintering is the limited selection of materials currently available for use compared with more conventional processes such as injection moulding. This constrains the usefulness of the technology for designers and engineers. A primary reason for this is a lack of detailed understanding of the development process for new materials for laser sintering. This PhD investigation examines some of the key attributes and requirements needed for successfully implementing new polymer-based laser sintering materials. A strategic method for characterizing and identifying new polymer materials was created utilizing thermal measurements, practical and analytical methods to quantify sintering rate, and degradation studies. Validation of this work occurred through the successful integration of a new laser sintering material at industrial project partner Burton Snowboards. Thermal degradation as a result of the laser sintering process was studied in detail and resulted in the creation of a proposed new parameter: Stable Sintering Region (SSR). The term acknowledges and defines the region above the melting point that is the minimum requirement for sintering to occur and an upper limit beyond which polymer deterioration impedes on mechanical properties. A quantitative approach to define the SSR was developed and explored with three different laser sintering materials, two of which were flexible elastomers. The ability to specifically interpret laser sintering process parameters from thermal degradation characterization was created and used to explore the effects of high energy input on tensile properties and molecular weight. The results of these tests showed the potential to identify an Optimum Sintering Range based on maximizing mechanical properties through the control of energy input and molecular weight. This thesis makes a significant contribution to the knowledge and understanding of polymer laser sintering, especially in the context of materials development. Novel concepts such as the Stable Sintering Region were developed using a theoretical approach and practical measurements and were also thoroughly explored for verification. Additionally, a new method to use a powder characterization technique to predict the actual machine parameters of a material in the laser sintering process was quantified. This has several implications for testing new materials for laser sintering and efficiently identifying appropriate processing conditions.

Thesis (M.S.)--West Virginia University, 2006.<br>Title from document title page. Document formatted into pages; contains xi, 87 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 86-87).

Epoxy nanofiltration membranes were synthesized using a diamine and a diepoxide in a one-pot step polymerization. These membranes were stable in organic solvents and used for chemical separations in dichloromethane. The epoxy membranes showed excellent selectivities in chemical separations of over 100:1. The selectivity of the membrane was optimized by adding in a triepoxide to the polymerization to increase the cross-link density. Optimization of the membranes increased the selectivity up to 250:1 for select chemical separations. These epoxy membranes are some of the first nanofiltration membranes used in the separation of important fatty acids such as omega-3 fish oil fatty acid ethyl esters, and saturated fatty acid methyl esters. The epoxy membranes can separate eicosahexaenoic acid ethyl ester from docosahexenoic acid ethyl ester with selectivities up to 1.4:1. The selectivity of saturated fatty acid methyl esters with epoxy membranes were as high as 100:1 for the separation of methyl butyrate from methyl stearate. Epoxy membranes are also the first stimulus-responsive membranes with a disulfide-bond dependent mechanism. The labile disulfide bond is cleaved upon exposure to a chemical stimulus, which cleaves the cross-links within the membrane, and increases the pore size. The flux and selectivity of chemicals through the membrane was controlled before and after exposure to a chemical stimulus. The membranes were implemented in a multicomponent chemical separation to produce three-purity enriched fractions from a three-component mixture. The purity of chemicals improved from 33% up to 82%, with recovery yields as high as 88%.

Wood plastic composites (WPCs) were made using matrices of recycled high-density polyethylene (rHDPE) and polypropylene (rPP) with sawdust (Pinus radiata) as filler. Corresponding WPCs were also made using virgin plastics (HDPE and PP) for comparison with the recycled plastic based composites. WPCs were made through melt compounding and hot-press moulding with varying formulations based on the plastic type (HDPE and PP), plastic form (recycled and virgin), wood flour content and addition of coupling agent. The dimensional stability and mechanical properties of WPCs were investigated. Durability performances of these WPCs were studied separately, by exposing to accelerated freeze-thaw (FT) cycles and ultraviolet (UV) radiation. The property degradation and colour changes of the weathered composites were also examined. Dimensional stability and flexural properties of WPCs were further investigated by incorporation of nanoclays in the composite formulation. To understand the changes in WPCs stability and durability performance, microstructure and thermal properties of the composites were examined. Two mathematical models were developed in this work, one model to simulate the moisture movement through the composites in long-term water immersion and the other model to predict the temperature profile in the composites during hot-press moulding. Both rHDPE and rPP matrix based composites exhibited excellent dimensional stability and mechanical properties, which were comparable to those made from virgin plastics. Incorporation of maleated polypropylene (MAPP) coupling agent in composite formulation improved the stability and the mechanical properties. The incorporation of 3 wt. % MAPP coupling agent to WPCs showed an increase in tensile strength by 60% and 35 %, respectively, for the rHDPE based and rPP based composites with 50 wt. % wood flour. Scanning electron microscopy (SEM) images of the fractured surfaces of WPCs confirmed that the MAPP coupling improved the interfacial bonding between the plastic and the wood filler for both series of composites. Long-term water immersion tests showed that the water transport mechanism within the WPCs follows the kinetics of Fickian diffusion. Dimensional stability and flexural properties of the WPC were degraded after 12 accelerated FT cycles as well as 2000 h of UV weathering for both recycled and virgin HDPE and PP based composites. However, the MAPP coupled composites had improved stability and flexural property degradation. The surface of the weathered composites experienced a colour change, which increased with the exposure time. The MAPP coupled composites exhibited less colour change as compared to non-coupled composites. Regarding the effect of the plastic type, the PP based composites experienced higher colour change than those based on HDPE. With weathering exposure, flexural strength and stiffness of the WPCs were decreased, but elongation at break was increased regardless of plastic type and wood flour content. MAPP coupled rPP and rHDPE based UV weathered WPCs lowered the degradation of stiffness by 50% and 75%, respectively compared to non-coupled WPCs. SEM images of the fractured surfaces of FT and UV weathered WPCs confirmed a decrease in the interfacial bonding between the wood flour and matrix. Thermal properties of weathered composites changed with weathering, but the extent of the changes depended on WPCs formulation and matrix type. From the experimental studies on nanoclay-filled rHDPE composites, it is found that stability, flexural properties of WPCs could be improved with an appropriate combination of coupling agent, and nanoclay contents processed by melt blending. Incorporation of 1-5 wt. % nanoclay in the maleated polyethylene (MAPE) coupled wood plastic composite improved the dimensional stability and flexural properties. The thermal properties changed with the addition of nanoclay and MAPE in WPCs. In this work, a hot press-moulding model was proposed based on the one-dimensional transient heat conduction to predict the temperature profile of the WPCs during hot pressing cycle. The results from this work clearly show that rHDPE and rPP can be successfully used to produce stable and strong WPCs, which properties and performances are similar to or comparable to composites made of wood and virgin plastics. Therefore, WPCs based on recycled PP and HDPE matrix could have potential to use as construction materials.

The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers (CPs). However, the high cost and toxicity of applicable metal oxides and poor long term stability of CPs paved the way to alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and CPs could significantly reduce the cost of supercapacitor electrodes compared to metal oxides. Recent developments in carbon allotropes, such as carbon nanotubes (CNTs) and especially graphene (G), have found applications in supercapacitors because of their enhanced double layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties. The main objective of the research presented in this dissertation is to increase the energy density of supercapacitors by the development of nanocomposite materials composed of graphene and different CPs, such as: (a) polyaniline derivatives (polyaniline (PANI), methoxy (-OCH3) aniline (POA) and methyl (-CH3) aniline (POT), (b) poly(3-4 ethylenedioxythiophene) (PEDOT) and (c) polypyrrole (PPy). The research was carried out in two phases, namely, (i) the development and performance evaluation of G-CP (graphene in conducting polymers) electrodes for supercapacitors, and (ii) the fabrication and testing of the coin cell supercapacitors with G-CP electrodes. In the first phase, the synthesis of different morphological structures of CPs as well as their composites with graphene was carried out, and the synthesized nanostructures were characterized by different physical, chemical and thermal characterization techniques, such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV-visible spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, BET surface area pore size distribution analysis and Thermogravimetric Analysis (TGA). The electrochemical properties of G-CP nanocomposite-based supercapacitors were investigated using Cyclic Voltammetry (CV), galvanostatic charge-discharge and Electrochemical Impedance Spectroscopy (EIS) techniques in different electrolytes, such as acidic (2M H2SO4 and HCl), organic ( 0.2 M LiClO4) and ionic liquid (1M BMIM-PF6) electrolytes. A comparative study was carried out to investigate the capacitive properties of G-PANI derivatives for supercapacitor applications. The methyl substituted polyaniline with graphene as a nanocomposite (G-POT) exhibited a better capacitance (425 F/g) than the G-PANI or the G-POA nanocomposite due to the electron donating group of G-POT. The relaxation time constants of 0.6, 2.5, and 5s for the G-POT, G-PANI and G-POA nanocomposite-based supercapacitors were calculated from the complex model by using the experimental EIS data. The specific capacitances of two-electrode system supercapacitor cells were estimated as 425, 400, 380, 305 and 267 F/g for G-POT, G-PANI, G-POA, G-PEDOT and G-PPy, respectively. The improvements in specific capacitance were observed due to the increased surface area with mesoporous nanocomposite structures (5~10 nm pore size distribution) and the pseudocapacitance effect due to the redox properties of the CPs. Further, the operating voltage of G-CP supercapacitors was increased to 3.5 V by employing an ionic liquid electrolyte, compared to 1.5 V operating voltage when aqueous electrolytes were used. On top of the gain in the operating voltage, the graphene nano-filler of the nanocomposite prevented the degradation of the CPs in the long term charging and discharging processes. In the second phase, after studying the material's chemistry and capacitive properties in three-electrode and two-electrode configuration-based basic electrochemical test cells, coin cell type supercapacitors were fabricated using G-CP nanocomposite electrodes to validate the tested G-CPs as devices. The fabrication process was optimized for the applied force and the number of spacers in crimping the two electrodes together. The pseudocapacitance and double layer capacitance values were extracted by fitting experimental EIS data to a proposed equivalent circuit, and the pseudocapacitive effect was found to be higher with G-PANI derivative nanocomposites than with the other studied G-CP nanocomposites due to the multiple redox states of G-PANI derivatives. The increased specific capacitance, voltage and small relaxation time constants of the G-CPs paved the way for the fabrication of safe, stable and high energy density supercapacitors.

Since the discovery of carbon nanotubes (CNTs) and nanoclays, there has been a great deal of research conducted for uses in applications such as: energy storage, molecular electronics, structural composites, biomedical to name but a few. Owing to their unique intrinsic properties and size means that they have an ever growing potential in the consumer and high technology sectors. In recent years the concept of using these as fillers in polymers has shown great potential. One such function is, as flame retardant additives. These possess much better environmental credentials than halogenated based additives as well as only needing to use a small loading content compared to traditional micron sized fillers. The combination of the above make these fillers ideal candidates for polymers and their composites. Especially with regards to natural fibre composites. Owing to environmental awareness and economical considerations, natural fibre reinforced polymer composites seem to present a viable alternative to synthetic fibre reinforced polymer composites such as glass fibres. However, merely substituting synthetic with natural fibres only solves part of the problem. Therefore selecting a suitable material for the matrix is key. Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33 % of all plant matter is cellulose; i.e. the cellulose content of cotton is 90 % and that of wood is 50 %. However just like their synthetic counterparts, the poor flame retardancy of bio-derived versions restricts its application and development in important fields such as construction and transportation. Abstract -vi- Traditional methods to improve the flame retardancy of polymeric material involve the use of the micron sized inorganic fillers like ammonium polyphosphate (APP) or aluminium trihydroxide (ATH). Imparting flame retardancy with these inorganic fillers is possible but only with relatively high loadings of more than 50 wt. %. This causes detrimental effects to the mechanical properties of the composite and embrittlement. Applying nanofillers can achieve similar if not better flame retarding performances to their micron sized counterparts but at much lower loading levels (<10 wt.%), thus preserving better the characteristics of the unfilled polymer such as good flow, toughness, surface finish and low density. This is the main focus of this study and it will be achieved by using various experimental techniques including the cone calorimeter and the newly developed microcalorimeter. After a comprehensive literature survey (Chapter 2), the experimental part of the thesis starts with a feasibility study of a flame retardant natural reinforced fibre sheet moulding compound (SMC) (Chapter 3). This work demonstrated that with a suitable flame retardant the peak heat release rate can be reduced. Chapter 4 deals with further improving the flame retardancy of the previously used unsaturated polyester resin. The aim is to study any synergistic behaviour by using aluminium trihydroxide in conjunction with ammonium polyphosphate whilst testing in the cone calorimeter. In Chapter 5, nanofillers are used to replace traditional micron sized fillers. In unsaturated polyester, multi-walled carbon nanotubes and sepiolite nanoclay are used together to create a ternary polymer nanocomposite. The microcalorimeter was employed for screening of the heat release rate. This work showed that the ternary nanocomposite showed synergistic behaviour with regards to significantly reducing the peak heat release rate. Abstract -vii- The same nanofillers were utilised in Chapters 6 and 7 but this time in combination with a thermoplastic (polypropylene) and bio-derived polymer (polylactic acid), respectively. In both systems an improved flame retardancy behavior was achieved whist meeting the recyclability objective. Chapter 8 attempts to show how the optimised natural fibre composite would behaviour in a large scale fire test. The ConeTools software package was used to simulate the single burning item test (SBI) and to classify the end product. This is a necessity with regards to commercialising the product for consumer usage. Finally, Chapter 9 is a summary of the work carried out in this research as well as possible future work that should be conducted.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Nie, Shuming; Committee Member: Bao, Gang; Committee Member: Chung, Leland; Committee Member: Murthy, Niren; Committee Member: Prausnitz, Mark.

With industries aiming at higher efficiencies, lightweight parts, and easier manufacturability there has been a recent trend of replacing the metallic materials with polymeric materials and its composites. Particularly in the automotive industry, there is a demand of replacing metallic material of bushes and bearings with polymer based materials (PBM). For these heavy performance requirements (as in automobiles), the commonly used industrial polymers like Acetal and Nylon fail to provide good mechanical and tribological performance. High-performance polymer like Polyphenylene Sulfide (PPS) is a relatively newer material and shows a potential of being a PBM alternative for metallic bearings in automobiles if their tribological performance can be improved.  One of the ways of improving the tribological performance of the polymer is by the addition of filler material, hence making a polymer composite. In this study, we used Short Carbon Fibre as micro-reinforcement material and Nano-diamonds and Graphene Oxide as nano-reinforcement material to make PPS composites. The varying mechanical and tribological behaviour of PPS composites with different weight percentage of reinforcement materials was investigated. The optimum composition of the reinforcement materials was identified, which resulted in significant improvement in mechanical and tribological properties of the base material.