Дисертації з теми "Polymeric layer"
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Authimoolam, Sundar Prasanth. "STABILITY OF AFFINITY BASED LAYER-BY-LAYER POLYMERIC SELF-ASSEMBLIES FOR ORAL WOUND APPLICATIONS." UKnowledge, 2011. http://uknowledge.uky.edu/cme_etds/3.
Анотація:
Oral mucositis is a painful and debilitating chronic inflammatory condition that can result from chemo and/or radiotherapy. While current treatment strategies which provide temporary relief exist, there is still an unmet clinical need for a robust long active barrier strategy which can simultaneously provide protection and release drug to enhance the wound healing response. It is proposed that an affinity based layer-by-layer self-assembled barrier administered as a series of mouth rinses can allow for wound specific drug delivery, providing an effective regenerative therapy.
In this work, biotinylated poly(acrylic acid) is used to develop LBL assemblies based upon biotin-streptavidin affinity interactions. To explore the ability of developed LBL assemblies to resist the harsh intraoral environment, in vitro chemical and ex vivo mechanical tests are performed. The stability results demonstrate significant LBL barrier stability with wear resistance. From principal component regression analysis, factors such as polymer MW and number of layers in assemblies contributed significantly to chemical barrier stability. Also it is observed that the extent of biotin conjugation plays a significant role in LBL development and in mechanical stability. Thus, the proposed affinity based multilayered assemblies with their excellent barrier properties offer a modular treatment approach in oral mucosal injuries.
2
Zhao, Li. "Fabrication of polymeric microcarriers with reduced permeability using layer-by-layer, surface-initiated polymerization and emulsion techniques." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24853.
Анотація:
In recent years, polymeric microcarriers have drawn great attention because of their potential applications in medical, cosmetic and some other industries. A variety of materials, preparation techniques have been explored to endow these microcarriers the desired properties. In spite of encouraging improvements in other properties, the low permeability of microcarriers remains a challenge which results in massive amount of cargo loss due to fast release. This work aimed to develop microcarriers with reduced permeability by coating with biocompatible and hydrophobic polymers via different techniques such as Layer-by-Layer, surface-initiated atom transfer radical polymerization and emulsion methods. This thesis starts with an introduction and literature review, which present the background of this work, followed by the description of materials as well as methods used in this work in chapter 3. Chapter 4 studied various parameters for fabricating structurally intact Poly(lactic acid) stereocomplex microcapsules, and demonstrated that heat treatment could significantly reduce the permeability of PLA microcapsules. In chapter 5, Layer-by-Layer and surface-initiated atom transfer radical polymerization techniques were combined to fabricate PMMA coated microparticles with low permeability. A polyelectrolyte macroinitiator and Poly(sodium 4-styrenesulfonate) were first deposited onto CaCO3 particles through LbL process, followed by growing PMMA brush layer via ATRP from the polyelectrolyte precursor. Chapter 6 introduced a simple emulsion method to prepare PLA coated CaCO3 microparticles with low permeability, which can retain bioactive molecules within the particles. It was found that 0.8 was the optimal CaCO3/PLA mass ratio in terms of the low permeability of microparticles as well as high-usage of polymers. In chapter 7, PLA films were synthesized from two different types of macroinitiators, with one being polyelectrolyte based and the other one being Poly(2-hydroxyethyl methacrylate) polymer brush precursor. The kinetics of PLA film growth from different precursors was compared whilst degradation of PLA films was also studied.
3
Lin, Xiaofeng. "Toward nanofiltration membranes with layer-by-layer assembled and nano-reinforced separation layers." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE012/document.
Анотація:
Ce travail de thèse a été consacré à l'élaboration d'un nouveau type de membranes de nanofiltration efficaces avec des propriétés améliorées (flux élevé et rétention élevée, et de bonnes propriétés mécaniques) en déposant un revêtement assemblé couche-par-couche (LbL) sur des supports poreux. Après avoir systématiquement étudié le mécanisme de croissance des films assemblés couche par couche des polyélectrolytes choisis et la relation entre les structures de ces films et les performances des membranes résultant, nous avons identifié avec succès les meilleures structures multicouches pour la construction de membranes de nanofiltration de référence avec des performances optimales. En outre, en prenant avantage de la technique LbL, nous avons introduit une couche de diffusion latérale assemblée soit de nanofibrilles de cellulose ou de nanotubes de carbone, qui permet d’augmenter le flux de 30% tout en conservant la même rétention par rapport à la membrane de référence. En plus, les films assemblés à base de chitosan et nanofibrils de cellulose ont montré une forte résistance à la traction allant jusqu’à 450 MPa et un module d’Young jusqu’à 50 GPaThis thesis work was devoted to the development of a novel and efficient nanofiltration membrane with improved properties (high flux and high retention, good mechanical strength) by coating Layer-by-Layer (LbL) assembled films onto porous membrane support. After having systematically studied the growth mechanism of LbL-assembled films of chosen polyelectrolytes and the relationship between the structures of these films and the membrane performance of the resulting NF membranes, we successfully identified the best multilayer structures for constructing nanofiltration membranes (NF) of reference with optimal membrane performance. Furthermore, taking advantages of the LbL-assembly, we successfully introduced LbL-assembled lateral diffusion layer that is made of either cellulose nanofibrils or carbon nanotubes, which in turn led to membranes with 30% higher flux. In addition, the LbL-assembled films of chitosan and cellulose nanofibrils showed surprisingly strong tensile strength of up to 450 MPa and a high Young modulus of up to 50 GPa
4
Guzy, Matthew Thomas. "Organic Self-Assembled Layer-by-Layer Thin Films for Second-Order Nonlinear Optics." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28852.
Анотація:
Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate.
The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of &967;(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices.
In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation. The effect of adding ionic salts to the dye solutions was studied, with hopes of increasing the chromophore density in the film by shielding inter-dye electrostatic repulsions. A linear relationship in deposited amount, as characterized by absorbance/bilayer, was observed as the salt concentration was increased. Little effect on &967;(2) was observed for films made with the as-received Procion Red MX-5B chromophore. However, films fabricated from purified Procion Brown MX-GRN showed a definite dependence on added salt. Exceptional &967;(2) values were obtained for Procion Brown films deposited using 0.5 M NaCl and PAH. The importance of depositing from non-aggregated solutions was again highlighted, as films made with the less soluble Procion Orange were significantly less homogeneous than those made from Procion Red and Procion Brown which were highly soluble. The role of polycation structure on the deposition and orientation of Procion Brown and Red was examined.Ph. D.
5
Ogbomo, Sunny Minister D'Souza Nandika Anne. "Processing, structure property relationships in polymer layer double hydroxide multifunctional nanocomposites." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/ark:/67531/metadc12174.
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Ogbomo, Sunny Minister. "Processing, structure property relationships in polymer layer double hydroxide multifunctional nanocomposites." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12174/.
Анотація:
Dan Beaty (1937-2002) was a prolific composer, pianist, researcher, educator, and writer. His large compositional output included chamber works, choral works, songs, orchestral pieces, electronic music, and keyboard works. Beaty was well versed in traditional Western music as well as the more avant-garde and perplexing idioms of the twentieth century. Beaty's compositions reflect the many fascinating, if not always popular, musical trends of his time. His music encompasses styles from serial to jazz, shows compositional influences from Arnold Schoenberg to Indonesian music, and demonstrates thought-provoking and highly intellectual craftsmanship. This document explores several of Beaty's songs through a discussion of the composer's life and compositional process. Songs included in this document are Three Weeks Songs, October, November, A Sappho Lyric, Love Song, That Night When Joy Began, and War Lyrics. This document was written to accompany the author's DMA Lecture-Recital at the University of North Texas. Unfortunately, Beaty's vocal music was never published and is mostly unknown. One goal of the project was to initiate interest in Beaty's songs. Through this document, Lecture-Recital, and additional performances, considerable strides have been made to bring Beaty's songs to new audiences throughout the United States. In addition, the author has received permission from the Beaty family to publish Dan Beaty's songs.
7
Wang, Dong. "The Application of Thin Film Ionic Self-assembled Multilayer (ISAM) Nanostructures in Electromechanical Bending Actuators and Micro-fabricated Gas Chromatography (uGC) Devices." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51186.
Анотація:
Ionic self-assembled multilayer (ISAM) thin film nanostructures, including highly porous and conductive gold nanoparticles (GNP), and highly porous and thermally stable silica nanoparticles (SNP), were fabricated via the layer-by-layer (LbL) self-assembly technique. Their application in ionic polymer-metal composite (IPMC) electromechanical bending actuators and microfabricated gas chromatography (microGC) devices were investigated and significant performance improvements of these devices were achieved.
IPMC bending actuators, consisting of an ionic electroactive polymer (iEAP) membrane as backbone, ionic liquids (IL) as electrolyte, and ISAM GNP thin film as porous electrode, were fabricated and investigated. The influences of humidity, conductive network composite (CNC), and IL uptake on the bending performance were examined and discussed. An equivalent circuit model to simulate both the electrical and mechanical responses was also proposed and experimentally verified. Moreover, IPMC actuators made from other newly synthesized iEAP membranes were fabricated and tested. Some of them showed promising performance that was comparable or even better as compared to the ones made from Nafion.
LbL fabricated ISAM SNPs thin film coatings were also applied in the microGC devices including micro fabricated thermal preconcentrators (microTPC) and separation columns (microSC) as adsorbent and stationary phase materials, respectively. New fabrication approaches were developed to selectively coat uniform conformal ISAM SNP coatings in these devices with different 3D microstructures. Thus, functionalized microTPCs and microSCs showed good performance, which can be further improved by using the ISAM SNPs coating as a nanotemplate for modifying additional polymer adsorbents or as the anchor sites for incorporating functional molecules for targeting detection.Ph. D.
8
Njomo, Njagi. "Synthesis of sulphonated and transition metal oxide doped polymeric nanocomposites for application in design of supercapacitors." University of the Western Cape, 2011. http://hdl.handle.net/11394/5429.
Анотація:
Philosophiae Doctor - PhDTo meet a fast-growing market demand for next generation portable electronic devices with higher performance and increased device functionalities, efficient electrical energy devices with substantially higher energy, power densities and faster recharge times such as supercapacitors are needed. The overall aim of this thesis was to synthesize nanostructured sulphonated polyaniline and transition metal single, binary and ternary mixed oxide doped nanocomposites with electro-conductive properties. These nanocomposites were anchored on activated graphitic carbon and used in design of asymmetric supercapacitors. Tantalum(IV)oxide, tantalum(IV)oxide-nickel(II)oxide, tantalum(II)oxide-manganese(III)oxide, tantalum(II)oxide-nickel(II)oxide-manganese(II,III)oxide nanoparticles were synthesised using modified sol-gel methods. These were then dispersed, individually, in acidic media through sonication and incorporated in-situ into the polymeric matrix during the oxidative chemical polymerization of aniline doped with poly(4-styrene sulphonic acid). These novel polymeric nanocomposites were characterised with FTIR, UV-visible, TEM, SEM, EDS, XRD to ascertain successful polymerization, doping, morphology and entrapment of the metal oxide nanoparticles. SECM approach curves and interrogation of CV revealed that these nanocomposites are conductive and electro-active. The cells showed good supercapacitor characteristics with high specific capacitances of 170.5 Fg⁻¹ in TaO₂- PANi-PSSA, 166.1 Fg⁻¹ in TaO₂-NiO-PANi-PSSA, 248.4 Fg-1 in TaO-Mn₂O₃-PANi- PSSA and 119.6 Fg⁻¹ in TaO-NiO-Mn₃O₄-PANi-PSSA. Their corresponding energy densities were calculated as 245.5 Whg⁻¹, 179.4 Whg⁻¹, 357.7 Whg⁻¹ and 172.3 Whg⁻¹ respectively. They also gave respective power densities of 0.50 Whg⁻¹, 0.61 Whg⁻¹, 0.57 Whg⁻¹ and 0.65 Whg⁻¹ and showed good coulombic efficiencies ranging between 77.97% and 83.19%. These materials are found to have a long cycle life and therefore good electrode materials for constructing supercapacitor cells.
National Research Foundation (NRF)
9
Ripollés, Sanchis Teresa. "Interfacial and Bulk Operation of Polymeric Solar Cells by Optoelectronics and Structural Techniques." Doctoral thesis, Universitat Jaume I, 2014. http://hdl.handle.net/10803/277095.
Анотація:
This Ph.D. Thesis focuses on the investigation of organic photovoltaic (OPV) technology, especially in aspects of experimental device processing, and optoelectronic and electrical characterization on OPV devices to be readily marketable. More specifically, the topics addressed are the following: origin of recombination current,open-circuit voltage and crystallinity, transport driving force, contact selectivity and interface states, alternative hole transporting layers and oxygen and degradation routes.
10
Serpe, Michael Joseph. "Self-Assembly of Poly(N-isopropylacrylamide) Microgel Thin Films." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4806.
Анотація:
The assembly of poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) microgel thin films into disordered and ordered arrays was investigated. Disordered pNIPAm-co-AAc microgel arrays were assembled based on electrostatic attractions between polyanionic pNIPAm-co-AAc microgels and polycationic poly(allylamine hydrochloride) (PAH). These interactions were studied in solution and subsequently used to assemble thin films following a Layer-by-Layer assembly protocol. Thin films were assembled as a function of pNIPAm-co-AAc microgel solution temperature and the resultant film thermoresponsivity characterized as a function of microgel layer number and pH. The response of assembled thin films to pH 3.0 and 6.5 exposure was then characterized by quartz crystal impedance and surface plasmon resonance spectroscopy, which showed that the thin film solvation was highly dependent on the pH of the solution it was in. Assembled thin films were also shown to be useful as controlled drug delivery platforms, where it was found that small molecules could be released from the films in a temperature regulated fashion. Microgel thin films also exhibited unique optical properties and were used as microlens arrays, which were able to focus pattern in air as well as in solution and had focal lengths that could be tuned in response to pH and temperature changes. Ordered microgel arrays were assembled following a thermal annealing process, in order to make light diffracting materials. These ordered arrays were photopolymerized and exhibited temperature dependent Bragg diffraction properties.
11
Pangilinan, Katrina Dayoan. "Layer-by-Layer and Photochemical Grafting of ATRP Initiators for Thermoresponsive Surfaces." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1448375686.
12
Pallotta, Arnaud. "Films polymériques pour le développement de stents innovants." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0192/document.
Анотація:
La prise en charge en urgence des pathologies ischémiques repose dans un premier temps sur la thrombolyse et/ou l’angioplastie puis dans un second temps sur des mesures hygiéno-diététiques. L’angioplastie consiste en la destruction de l’obstacle situé dans l’artère et elle est souvent suivie (dans 70 % des cas) par la pose d’une endoprothèse ou stent afin que le vaisseau lésé retrouve son diamètre. Malgré des innovations thérapeutiques (stents libérant des principes actifs), des problèmes de thrombose et de resténose au niveau du site lésé sont observés. Or, le monoxyde d’azote, NO, un gazotransmetteur de l’organisme, possède des propriétés intéressantes (antiagrégant plaquettaire, effet de recrutement des cellules endothéliales, effet antiprolifératif sur les cellules musculaires lisses) pour lutter contre ce phénomène, à concentration physiologique. Dans ce travail, nous avons développé une formulation innovante pouvant recouvrir un stent et étant capable de délivrer du NO. Il s’agira d’incorporer des nanoparticules d’or caractérisées par une capacité de greffage par un donneur de NO (AuNP@RSNO) très importante au sein des couches d’un film constitué de polyélectrolytes (polycations et polyanions interagissant de façon électrostatique). Ici, les AuNP sont considérées comme une matière première pharmaceutique. Une méthode de dosage et un contrôle qualité de ces dernières ont donc été développés. Les films créés présentent une stabilité importante (> 1 an) et sont capables d’immobiliser un grand nombre d’AuNP (1012 AuNP/cm²/cycle). Pour augmenter le taux de chargement des AuNP au sein des films, l’optimisation de leur construction a été réalisée. Plusieurs polycations ont été testés (chlorhydrate de poly(allylamine), poly(éthylène glycol) et poly(méthacrylate d’ester)) ainsi que deux milieux de dissolution différents (tampon phosphate et tampon Tris, à pH et concentrations identiques). Le meilleur rapport stabilité/taux de chargement a été atteint avec l’utilisation du chlorhydrate de poly(allylamine) et le tampon Tris. Enfin, les films ont présenté une inertie face à des protéines, des cellules et du sang total. Le système développé représente donc une forme adaptée pour être déposé à la surface de stentsEmergency management of ischemic pathologies is initially based on thrombolysis and / or angioplasty and secondly on hygiene-dietetic measures. Angioplasty consists of the destruction of the obstacle located in the artery and is often followed (in 70% of cases) by placing a stent so that the damaged vessel regains its diameter. Despite therapeutic innovations (drug eluting stents), problems of thrombosis and restenosis in the injured site are often observed. However, nitric oxide, NO, has interesting properties (platelet antiaggregant, endothelial cell recruitment effect, antiproliferative effect on smooth muscle cells) against this phenomenon at physiological concentration. In this work, we developed an innovative formulation that can deposited on a stent and that will be able to deliver NO. AuNP grafted with a high density of NO donors (AuNP@RSNO) will be incorporated in layer-by-layer films composed of polyelectrolytes (electrostatic interactions between polycations and polyanions) Here AuNPs are considered as a pharmaceutical raw material. A quantification method and a quality control of them were therefore developed. Created films created showed an important stability (> 1 year) and were able to immobilize a large number of AuNP (1012 AuNP/cm²/cycle). In order to increase the loading rate of AuNP films, optimization of their construction was carried out. Several polycations were tested (poly (allylamine hydrochloride), poly (ethylene glycol) and poly (methacrylate ester)) as well as two different dissolution media (phosphate buffer and Tris buffer, same pH and concentrations). The best stability/loading ratio was achieved with the use of poly (allylamine) hydrochloride and Tris buffer. Finally, the films showed inertness when they were exposed to proteins, cells and whole blood. The developed system is therefore well suited to be deposited on the surface of stents
13
Adlafi, Morwan. "Étude d’une protection pour le matériel embarqué du fantassin soumis à des projectiles de type fragment." Thesis, Lorient, 2021. http://www.theses.fr/2021LORIS614.
Анотація:
La protection du matériel électronique embarqué est devenue un enjeu majeur pour assurer la sécurité du combattant. On peut citer divers exemples tels que la protection des piles à hydrogène dans les véhicules ou dans la batterie embarquée d'un soldat. C'est dans ce contexte que s'inscrit la thèse, où une étude est menée sur une protection de type multi-couches, sollicitée par des projectiles de type fragment, de quelques kilogrammes, allant à des vitesses de l'ordre de 10 m/s. Afin d'assurer la mise en service de telles protections, des essais et des simulations doivent être menés sur un large champ de sollicitations. La littérature montre que les structures multi-couches offrent un bon compromis entre capacité à absorber l’énergie d’impact et légèreté. Le complexe étudié pour cette thèse est composé d’une couche métallique, acier ou aluminium, et d’une couche de polymère. La première partie de cette thèse est consacrée à la caractérisation des plaques métalliques étudiées pour cette thèse : acier DP450 et aluminium AA2024-T3. Un nouvel essai de cisaillement séquencé est proposé afin d’identifier le comportement de la tôle en grande déformation. L’essai de traction à déformation plane est adapté pour identifier la déchirure des tôles en dynamique, jusqu’à des vitesses de déformation de l’ordre de 200/s. La deuxième partie est consacrée à l’identification complète d’une nouvelle résine polydicyclopentadiene (PDCPD) appelée Nextene. Dans la dernière partie, différentes structures multicouches sont sollicitées par des impacts à l’aide d’une catapulte qui projette des projectiles de 2.5 kilogrammes à une vitesses de 10 m/s. Leurs comportements respectifs à l’impact sont comparés et simulés numériquementThe protection of onboard electronic equipment has become a major issue in ensuring the safety of the combatant. We can cite various examples such as the protection of hydrogen cells in vehicles or in a soldier's onboard battery. It is in this context that the thesis is being carried out, studying multi-layers type of protection, solicited by fragment-type projectiles, weighing a few kilograms and at speeds of the order of 10 m/s. In order to ensure the commissioning of such protections, tests and simulations must be carried out over a wide range of stress states. The literature shows that multi-layer structures offer a good compromise between the ability to absorb impact energy and lightness. The studied sandwich is composed of a metallic layer, steel or aluminium, and a polymeric layer. The first part of this thesis is devoted to the characterisation of two sheet metals, namely a DP450 steel and AA2024-T3 aluminium alloy. A new sequenced shear test is proposed to identify the behaviour of the plate at large strains. The plane strain tension test is adapted to identify the dynamic failure of the sheets at strain rate up to 200/s. The second part is devoted to the complete identification of a new PDCPD resin called Nextene. An experimental campaign is carried out in order to identify the parameters of the SAMP behaviour law in the LS-Dyna software. In the last part of the study, structures are subjected to impacts in a catapult, using a 2.5 kilogram projectile at a speed of 10 m/s. Various combinations of sandwiches are compared, and the numerical simulation of the tests is proposed
14
Hill, Jacob A. Hill. "SURFACE LAYER MATRIX-ASSISTED LASER DESORPTION IONIZATION TIME OF FLIGHT MASS SPECTROMETRY (SL-MALDI-TOF MS) ANALYSIS OF POLYMER BLEND SURFACE COMPOSITION." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1514479406062149.
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Lu, Kuan. "Optimization Of Sublimation Conditions for Surface Layer Matrix-assisted Laser Desorption Ionization Time of Flight Mass Spectrometry Imaging (SL-MALDI- Tof MSI) of Polymer Surfaces." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1524846943404769.
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Anderson, Virginia Rose. "Atomic Layer Deposition of Platinum Particles, Titanium Oxide Films, and Alkoxysilane Surface Layers." Thesis, University of Colorado at Boulder, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3621292.
Анотація:
Atomic Layer Deposition (ALD) is a an excellent technique for depositing conformal thin films on complex geometries in layer by layer fashion. The mechanisms of depositing TiO2, platinum, and ethoxysilane molecules were probed with in situ Fourier transform infrared (FTIR) in order to better understand and improve the process. Each of these studies involves TiO2.
There are many uses for thin films of titanium dioxide, a semiconductor and high dielectric material. Current Atomic Layer Deposition (ALD) of TiO 2 generally involves water or ozone, which can oxidize and corrode some substrates of interest. Ritala et al. successfully deposited an assortment of metal oxides using no water, but instead, metal alkoxides and metal halides as precursors. Presented is a study of ALD of titanium dioxide using titanium tetrachloride (TiCl4) and titanium tetraisopropoxide (TTIP). In situ Fourier transform infrared (FTIR) studies revealed that the mechanism for TiO2 ALD using titanium tetrachloride and titanium tetraisopropoxide changed with temperature. At temperatures between 250 and 300°, the isopropoxide species after TTIP exposures quickly underwent β-hydride elimination to produce TiOH species on the surface. The observation of propene by quadrupole mass spectrometry supported the β-hydride elimination reaction pathway. Deposition was investigated between 150 and 300° on substrates including zirconia, alumina, and silica. Quartz crystal microbalance results and X-ray reflectivity showed that the system grew 0.5–0.6 Å/cycle at 250° X-Ray photoelectron studies also confirmed TiO2 film growth.
In another aspect of ALD use, self-limiting chemistry assisted with terminating a surface with alkoxysilanes. Tire rubber contains additives such as carbon black or silica particles to provide strength. Although in theory Kevlar fibers would provide strength while lowering the density and increasing car fuel efficiency, in practice Kevlar fibers disperse only very poorly in the rubber, leading to inhomogeneity. In order the increase the mixing likelihood between rubber and Kevlar, the reactions of some sulfurous siloxanes were examined on both aluminum oxide and titanium oxide. The titanium oxide adhesion layer allowed the deposition of molecules on the surface that looked promising for improving mixing with rubber and decreasing the weight of tires.
Atomic layer deposition offers the possibility of more precision in platinum deposition. In a platinum deposition study, the nucleation and growth of non-conformal platinum on TiO2 and WOx powder using Pt(hfac) 2 and formalin was examined with in-situ FTIR and transmission electron microscopy (TEM). Interest in substitution of Pt/C as the oxidation reduction reaction catalyst in polymer electrolyte membrane fuel cells (PEMFCs) led to the ALD synthesis of Pt/WOx and Pt/TiO2. A nucleation period on the order of 100 cycles was observed, after which, platinum loading and particle size measurably increased with increasing cycle number. The adsorption of the hfac ligand on the metal oxide substrate effectively inhibits nanoparticle coalescence during the growth phase, which led to further investigation of its use as a site-blocking agent. The results showed that Pt particle distance could be increased with the use of hfacH.
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Liu, Boer. "THERMAL ANNEALING EFFECT ON UNENTANGLED STAR-SHAPED POLYSTYRENE RESIDUAL LAYER." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525261861391343.
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Clarke, Christopher John. "The structure and kinetics of formation of grafted polymer layers." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320014.
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Hongming, Guo. "IMPROVING MATRIX DEPOSITION FOR SURFACE LAYER MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRY IMAGING (SL-MALDI-TOF MSI)." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron155654549756264.
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Pareek, Pradeep. "Photo-crosslinked Surface Attached Thin Hydrogel Layers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1115623310082-44480.
Анотація:
Stimuli sensitive polymers and hydrogels respond with large property changes to small physical and chemical stimuli (e.g. temperature, pH, ionic strength). The bulk behavior of these polymers is widely studied and they show an isotropic swelling. However, thin hydrogel layers of polymers on a substrate show a swelling behavior, which is constrained in some way. Therefore, size, confinement, patternability, response time and transition temperature of thin hydrogel layers are the most important parameters in technological applications and this study focuses on the investigation of these above-mentioned parameters. The aim of this study involves synthesis, characterization and application of thin photo-crosslinked hydrogel layers. Dimethylmaleimide (DMI) moiety was incorporated in the polymers chains and was used to introduce photo-crosslinking by [2+2] cyclodimerization reaction in the presence of UV irradiation. The following photo-crosslinkers based on DMI group were synthesized ? - Acrylate photo-crosslinker (DMIAm) - Acrylamide photo-crosslinker (DMIAAm) - Polyol photo-crosslinker (DMIPA, DMIPACl) The conventional free radical polymerization of above listed photo-crosslinker with its respective monomer resulted in formation of photo-crosslinkable polymers of (a) HEMA, (b) DMAAm, (c) NIPAAm/DMAAm, (d) NIPAAm/Cyclam. The properties of these polymers were investigated by NMR, UV-VIS spectroscopy, GPC and SPR. Thin hydrogel layers were prepared by spin coating on gold-coated LaSFN9 glass. The covalent attachment to the surface was achieved through an adhesion promoter. Swelling behavior of the thin polymer layers was thoroughly investigated by Surface Plasmon Resonance (SPR) Spectroscopy and Optical Waveguide Spectroscopy (OWS). SPR and OWS gave a wide range of information regarding the film thickness, swelling ratio, refractive index, and volume degree of swelling of the thin hydrogel layer. For hydrophilic photo-crosslinked hydrogel layers of HEMA and DMAAm, it was observed that the volume degree of swelling was independent of temperature changes but was dependent on the photo-crosslinker mol-% in the polymer. These surface attached thin hydrogel layer exhibited an anisotropic swelling. For NIPAAm photo-crosslinked hydrogel layers with DMAAm as a hydrophilic monomer, it was observed that both transition temperature (Tc) and volume degree of swelling increases with increase in the mol-% of DMAAm. To study the effect of film thickness on Tc and volume degree of swelling, hydrogels with wide range of film thickness were prepared and investigated by SPR. These results provided vital information on the swelling behavior of surface attached hydrogel layer and showed the versatility of SPR instrument for studying thin hydrogel layers. Later part of project involved synthesis of multilayer hydrogel assembly involving a thermoresponsive polymer and a hydrophilic polymer. The combination of two layers with photo-crosslinkable DMAAm polymer as base layer and photo-crosslinkable NIPAAm polymer as top layer formulate a multilayer assembly where, the base layer only swells in response to temperature and the top layer shows temperature dependent swelling. Photo-crosslinked hydrogel layers of NIPAAm, DMAAm and HEMA shows a high-resolution patterns when irradiated by UV light through a chromium mask. At last this study focused on an important application of these hydrogel layers for cell attachment processes. Cell growth, proliferation and spreading shows a biocompatible nature of these hydrogel surfaces. Such thermoresponsive photo-crosslinkable multilayer structure forms bases for future projects involving their use in actuator material and cell-attachment processes.
21
Huang, Heqing. "TETHERED POLYMERS: KINETICS AND CONTROL." Lexington, Ky. : [University of Kentucky Libraries], 2004. http://lib.uky.edu/ETD/ukymsen2004d00172/tether.pdf.
Анотація:
Thesis (Ph. D.)--University of Kentucky, 2004.Title from document title page (viewed Jan. 6, 2005). Document formatted into pages; contains xii, 162p. : ill. Includes abstract and vita. Includes bibliographical references (p. 149-161).
22
Motornov, Mikhail. "Fabrication and Study of Switchable Polymer Layers with Hydrophobic/Hydrophilic Behavior." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1101369711031-72233.
Анотація:
The framework of this thesis aims to fabricate materials, which change surface characteristics in response to environmental conditions. This response may be employed to improve material characteristics as adhesion, wettability, interaction with cells etc. The mixed brushes introduce adaptive and switching behavior in different surrounding media. Two main approaches were employed to fabricate mixed polymer brushes: "grafting to" and "grafting from". Mixed PS/PVP polymer brushes were synthesized via step-by-step grafting of these two polymers from polyamide (PA) surfaces. NH3 plasma was used for the introduction of amino and OH functionalities on PA surfaces with following attachment of azo initiator of radical polymerizaton. The mixed brushes prepared on the surface of PA textiles combine both the switching effect and effect of composite surface (i.e. micrometer scale roughness) which substantially amplifies the switching range. Mixed polymer brushes prepared from P(S-b-2VP-b-EO) and P(S-b-4VP) block copolymers were grafted to both the flat surface of Si wafers and to the surface of silica nanoparticles via quaternization reaction of the pyridine nitrogen. This one step grafting technique has a substantial advantage over the multistep grafting of mixed polymer brushes. We have demonstrated that combination of the two level hierarchical organization of polymer films at macroscopic and nanoscopic levels resulted in the formation of self adaptive surfaces switchable in controlled environment from ultra-hydrophobic to hydrophilic energetic states. The PFS/PVP mixed brush was grafted onto the pre-treated PTFE surface (plasma etching) with the needle like topography. The size of vertical needles was at micron scale. If the brush is switched to the hydrophobic state the layer has shown a unique ultra-hydrophobic behavior (complete non-wetting) with the contact angle approaching value of 160o. If the mixed brush was switched into the hydrophilic state the surface became completely wetted due to the capillary forces in the pores formed by the needle like structure. Thus, the surface can be either highly wettable or completely non-wettable with the self cleaning properties.
23
Jan, Chien Sy Jason. "Layer-by-layer assembly of electrically conductive polymer thin films." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/5979.
Анотація:
Layer-by-layer (LbL) assembly was used to produce highly conductive thin films
with carbon black (CB) and polyelectrolytes. The effects of sonication and pHadjustment
of the deposition mixtures on the conductivity and transparency of deposited
films were studied. Drying temperature was also evaluated with regard to thin film
resistance. Sonication and oven drying at 70oC produced films with the lowest sheet
resistance (~ 1500 é/sq), which corresponds to a bulk resistivity of 0.2 éâÂÂ
cm for a 14-
bilayer film that is 1.3 üm thick. Increasing the pH of the PAA-stabilized mixture and
decreasing the pH of the PEI-stabilized mixture resulted in films with 70% transparency
due to thinner deposition from increased polymer charge density. Varying the number
of bilayers allows both sheet resistance and optical transparency to be tailored over a
broad range.
Variation of deposition mixture composition led to further reduction of sheet
resistance per bilayer. A 14 bilayer film, made from mixtures of 0.25wt% carbon black
in 0.05wt% PAA and plain 0.1wt% PEI, was found to have a sheet resistance of
approximately 325 é/sq. Bulk resistivity was not improved due to the film being 8 üm
thick, but this combination of small thickness and low resistance is an order of magnitude better than carbon black filled composites made via traditional melt or
solution processing. Applications for this technology lie in the areas of flexible
electronics, electrostatic charge dissipation, and electromagnetic interference shielding.
24
Song, Hyunmin. "Melt-Processable Polymeric Photonic Crystals and Their Applications as Nanolayered Laser Films." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1333111539.
25
Tokarski, Tomasz. "Nanomechanical properties of nanocomposite polymer layer." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261161.
Анотація:
Interphase phenomenon gains more and more interest throughout the research community. An interphase is formed between a filler particle and a polymeric matrix, and it may constitute almost the entire volume of a nanocomposite. If the interphase have favorable mechanical properties it will thus result in a nanocomposite with such properties. Therefore, understanding the principles of its formation and properties are crucial in order to design advanced nanocomposites. This thesis focuses on PDMS-carboxylic acid modified latex nanoparticles (PDMS-CML) surface composites investigated by means of Atomic Force Microscopy (AFM). A new sample preparation method was designed and utilized together with the Gel Trapping Technique (GTT). Quantitative Imaging Mode and Contact Mode were utilized in the AFM studies. Topography and nanomechanical properties were investigated and compared for pure PDMS and PDMS containing the nanoparticles. Further, Contact Mode was used to investigate nanoscale wear of the samples in order to elucidate the interactions strength between the nanoparticles and the matrix.Egenskaper hos interfaser är ett område som röner allt större intresse hos forskarna inom materialområdet. En interfas bildas mellan en fillerpartikel och en polymermatris, och den kan utgöra den största volymen i en nanokomposit. Ifall interfasen har fördelaktiga mekaniska egenskaper så resulterar det alltså i att nanokompositen också får det. Det är därför viktigt att först principerna för hur interfasen bildas och får sina egenskaper om man vill framställa avancerade nanokompositer. I det här avhandlingsarbetet lades fokus på PDMS och karboxylsyrefunktionaliserade latex nanopartiklar som bildade en nanokomposit yta, vilken studerades med atomkraftsmikroskopi (AFM). En ny framställningsmetod togs fram och utnyttjades tillsammans med den så kallade ”Gel Trapping” tekniken (GTT). Quantitative Imaging och kontakt mode utnyttjades vid AFM studierna. Topografin och de nanomekaniska egenskaperna studerades för ren PDMS och PDMS blandat med nanopartiklarna. Nötning på nanometernivå studerades också, och dä med AFM i kontakt mode.
26
Dennis, Karla Ann. "Characterization of HFAPNB and PHOST as a polymer sensing layer in an interferometric evanescent wave sensor." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29682.
Анотація:
Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Henderson, Clifford L.; Committee Member: Ludovice, Pete; Committee Member: Ralph, Stephen E.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
27
Li, Wenqi. "Orderly Perforation of Polyester Films by Excimer Laser." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418332319.
28
Liao, Kang-Shyang. "Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3124.
29
Lee, Daeyeon. "Surface engineering using layer-by-layer assembly of pH-sensitive polymers and nanoparticles." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38979.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.Includes bibliographical references (p. 184-204).
Surface engineering of a variety of materials including colloidal particles and porous membranes has been achieved by using layer-by-layer assembly of pH-sensitive polymers and nanoparticles. In the first part of this thesis, hydrogen-bonded multilayer coatings comprising poly(acrylic acid) and polyacrylamide were used to functionalize spherical colloidal particles. Multilayer-modified colloids showed an excellent resistance to cell adhesion. Hydrogen-bonded multilayer coatings on microspheres also could be utilized as templates for in situ nanoparticle synthesis enabling the formation of nanoparticle-loaded hollow microcapsules. Silver nanoparticle-loaded multilayer coatings were created on magnetic microspheres to create antibacterial agents that can be manipulated using a magnetic field. In the second part, the surfaces of track-etched polycarbonate membranes were functionalized with multilayer coatings that undergo discontinuous swelling transition. Multilayers comprising poly(allylamine hydrochloride) and poly(styrene sulfonate) were deposited at a high pH condition (pH > 9.0). These multilayer-modified membranes exhibited hysteretic gating behavior that could be useful for the separation of pH-sensitive materials such as proteins.
(cont.) The growth and swelling behavior of the multilayers in the cylindrical pores of TEPC membranes were also investigated. Heterostructured magnetic nanotubes could be created by further modifying the multilayer-coated TEPC membranes. These magnetic nanotubes were utilized for the separation and controlled release of anionic molecules including active pharmaceutical ingredients. In the last part of this thesis, all-nanoparticle thin film coatings were created by sequentially depositing oppositely charged nanoparticles. The fundamental investigation of all-nanoparticle multilayers revealed that a narrow processing window exists in which multilayers of oppositely charged nanoparticles can be assembled in a true layer-by-layer manner. It was also demonstrated that structure and properties of all-nanoparticle thin films could be varied by controlling the assembly conditions. All-nanoparticle thin film coatings consisting of titanium oxide and silica nanoparticles exhibited potentially useful antifogging, antireflection and self-cleaning properties.
by Daeyeon Lee.
Ph.D.
30
Chen, Jing. "Novel H-bond donor polymers for layer-by-layer self-assembly multilayered films." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0087/document.
Анотація:
Ce travail est consacré à la synthèse de nouveaux polymères donneurs de liaison Hydrogène et à leur utilisation comme partenaire dans la construction de nouveaux films multicouches préparés par le procédé d’élaboration en couche-par-couche (LbL). Plus particulièrement, une nouvelle réaction impliquant des mercaptoalcools non protégés et le poly(2,3,4,5,6-pentafluorostyrène) (PPFS) a été développé et appliquée à la synthèse de nouveaux polymères donneurs de liaisons H. Ce couplage régiosélectif et chimiosélectif de type « click » avec un thiol hétérofonctionnel peut être utilisée pour préparer une bibliothèque de polymères qui diffèrent de par leur degré de substitution (DS) et/ou leur fonctionnalité en groupements associatifs. Le contrôle de ces paramètres structuraux permet de moduler leur force d’interactions avec des partenaires accepteurs de liaison H variés, comme la poly(4-vinyl pyridine) (P4VP), le poly(acrylate de n-butyle) (PBA) et le poly(oxyde d'éthylène) (PEO), de telle façon que tous les types de mélanges binaires (mélange non miscible, partiellement ou totalement miscible, ou complexe interpolymère) peuvent être obtenus. Ensuite, les dérivés de PPFS donneurs de liaisons H ont été utilisés en partenariat avec le P4VP pour élaborer avec succès de nouveaux films multicouche dont la force motrice est l’établissement de liaisons H. L'influence de nombreux paramètres relatifs à la structure des polymères donneurs (DS, structure chimique du groupement associatif), au type de modification chimique subie par le substrat sur lequel est élaboré le film multicouche (monocouche auto-assemblée vs. polymère greffée en conformation de type brosse) ou encore des paramètres expérimentaux liés aux conditions de dépôt (concentration des solutions de dépôt, nature du partenaire adsorbé en premier) a été étudiée. Plus particulièrement, le mécanisme de croissance ainsi que les caractéristiques de surface du film ont été évaluésThis work deals with the design of novel hydrogen-bond donor polymers and their use as partner in new tailor-made multilayered films prepared by the layer-by-layer (LbL) process. In this context, a novel regioselective and chemoselective “click-type” reaction of unprotected mercaptoalcohols onto poly(2,3,4,5,6-pentafluoro-styrene) (PPFS) has been developed, and applied to the synthesis of new hydroxylated H-bond donor polymers. This coupling with heterofunctional thiol is used to prepare a library of polymers differing in the degree of substitution (DS) and/or functionality. The fine control of these parameters makes it possible to tune their interaction ability with various acceptor polymers such as poly(4-vinyl pyridine) (P4VP), poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO), such that all possible scenarios (immiscible blend, partially or totally miscible blend or interpolymer complex) can be achieved. Subsequently, the resulting H-bond donor polymers (PPFS derivatives) were used to successfully build-up multilayered films with using P4VP as partner via layer-by-layer (LbL) through the dip deposition process. The influence of various parameters related to structure of the partners (DS, nature of the PPFS derivatives), the chemical structure of the surface onto which the film is built-up (self-assembled monolayer vs. polymer brush) and the deposition process (concentration of deposition solutions, nature of the first deposited partner) was in-depth evaluated, on both the growth mechanism and on the surface features of the multilayered films
31
Saikhwan, Phanida. "Cleaning behaviour of some polymeric and proteinaceous fouling layers." Thesis, University of Cambridge, 2008. https://www.repository.cam.ac.uk/handle/1810/252107.
32
Cheng, Kuan. "Magnet-assisted Layer-by-layer Assembly on Nanoparticles Based on 3D-printed Microfluidic Devices." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1554984796295339.
33
Zhong, Yingfan. "LAYER-BY-LAYER ROSE PETAL MIMIC SURFACE FOR OIL/WATER SEPARATIONS." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468441832.
34
Li, Bohao. "Room Temperature Processed Molybdenum Oxide Thin Film as a Hole Extraction Layer for Polymer Photovoltaic Cells." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1368015443.
35
Ivankovic, Alojz. "Rapid crack propagation in polymer multi-layer systems." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46837.
36
Sun, Qian. "Application of Polyelectrolyte Layer-By-Layer Self-Assembly on Polymer-Based Gene Delivery System." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519429.
37
Dekkers, Jan Matthijn. "Transparent conducting oxides on polymeric substrates by pulsed laser deposition." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57879.
38
Lee, Sangjin. "Structure-Property Relationships in Composite Layers Polymeric Film/Foam Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1473444646138984.
39
Carter, Jessica L. "Non-ionic highly permeable polymer shells for the encapsulation of living cells." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39529.
Анотація:
In this study, we introduce novel, truly non-ionic hydrogen-bonded layer-by-layer (LbL) coatings for cell surface engineering capable of long-term support of cell function. Utilizing the LbL technique imparts the ability to tailor membrane permeability, which is of particular importance for encapsulation of living cells as cell viability critically depends on the diffusion of nutrients through the artificial polymer membrane. Ultrathin, permeable polymer membranes are constructed on living cells without a cationic pre-layer, which is usually employed to increase the stability of LbL coatings. In the absence of the cytotoxic PEI pre-layer, viability of encapsulated cells drastically increases to 94%, as compared to 20-50% in electrostatically-bonded shells. Engineering surfaces of living cells with natural or synthetic compounds can mediate intercellular communication, render the cells less sensitive to environmental changes, and provide a protective barrier from hostile agents. Surface engineered cells show great potential for biomedical applications, including biomimetics, biosensing, enhancing biocompatibility of implantable materials, and may represent an important step toward construction of an artificial cell.
40
Fang, Peng. "Preparation and investigation of polymer-foam films and polymer-layer systems for ferroelectrets." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4841/.
Анотація:
Piezoelectric materials are very useful for applications in sensors and actuators. In addition to traditional ferroelectric ceramics and ferroelectric polymers, ferroelectrets have recently become a new group of piezoelectrics. Ferroelectrets are functional polymer systems for electromechanical transduction, with elastically heterogeneous cellular structures and internal quasi-permanent dipole moments. The piezoelectricity of ferroelectrets stems from linear changes of the dipole moments in response to external mechanical or electrical stress. Over the past two decades, polypropylene (PP) foams have been investigated with the aim of ferroelectret applications, and some products are already on the market. PP-foam ferroelectrets may exhibit piezoelectric d33 coefficients of 600 pC/N and more. Their operating temperature can, however, not be much higher than 60 °C. Recently developed polyethylene-terephthalate (PET) and cyclo-olefin copolymer (COC) foam ferroelectrets show slightly better d33 thermal stabilities, but usually at the price of smaller d33 values. Therefore, the main aim of this work is the development of new thermally stable ferroelectrets with appreciable piezoelectricity. Physical foaming is a promising technique for generating polymer foams from solid films without any pollution or impurity. Supercritical carbon dioxide (CO2) or nitrogen (N2) are usually employed as foaming agents due to their good solubility in several polymers. Polyethylene propylene (PEN) is a polyester with slightly better properties than PET. A “voiding + inflation + stretching” process has been specifically developed to prepare PEN foams. Solid PEN films are saturated with supercritical CO2 at high pressure and then thermally voided at high temperatures. Controlled inflation (Gas-Diffusion Expansion or GDE) is applied in order to adjust the void dimensions. Additional biaxial stretching decreases the void heights, since it is known lens-shaped voids lead to lower elastic moduli and therefore also to stronger piezoelectricity. Both, contact and corona charging are suitable for the electric charging of PEN foams. The light emission from the dielectric-barrier discharges (DBDs) can be clearly observed. Corona charging in a gas of high dielectric strength such as sulfur hexafluoride (SF6) results in higher gas-breakdown strength in the voids and therefore increases the piezoelectricity. PEN foams can exhibit piezoelectric d33 coefficients as high as 500 pC/N. Dielectric-resonance spectra show elastic moduli c33 of 1 − 12 MPa, anti-resonance frequencies of 0.2 − 0.8 MHz, and electromechanical coupling factors of 0.016 − 0.069. As expected, it is found that PEN foams show better thermal stability than PP and PET. Samples charged at room temperature can be utilized up to 80 − 100 °C. Annealing after charging or charging at elevated temperatures may improve thermal stabilities. Samples charged at suitable elevated temperatures show working temperatures as high as 110 − 120 °C. Acoustic measurements at frequencies of 2 Hz − 20 kHz show that PEN foams can be well applied in this frequency range. Fluorinated ethylene-propylene (FEP) copolymers are fluoropolymers with very good physical, chemical and electrical properties. The charge-storage ability of solid FEP films can be significantly improved by adding boron nitride (BN) filler particles. FEP foams are prepared by means of a one-step procedure consisting of CO2 saturation and subsequent in-situ high-temperature voiding. Piezoelectric d33 coefficients up to 40 pC/N are measured on such FEP foams. Mechanical fatigue tests show that the as-prepared PEN and FEP foams are mechanically stable for long periods of time. Although polymer-foam ferroelectrets have a high application potential, their piezoelectric properties strongly depend on the cellular morphology, i.e. on size, shape, and distribution of the voids. On the other hand, controlled preparation of optimized cellular structures is still a technical challenge. Consequently, new ferroelectrets based on polymer-layer system (sandwiches) have been prepared from FEP. By sandwiching an FEP mesh between two solid FEP films and fusing the polymer system with a laser beam, a well-designed uniform macroscopic cellular structure can be formed. Dielectric resonance spectroscopy reveals piezoelectric d33 coefficients as high as 350 pC/N, elastic moduli of about 0.3 MPa, anti-resonance frequencies of about 30 kHz, and electromechanical coupling factors of about 0.05. Samples charged at elevated temperatures show better thermal stabilities than those charged at room temperature, and the higher the charging temperature, the better is the stability. After proper charging at 140 °C, the working temperatures can be as high as 110 − 120 °C. Acoustic measurements at frequencies of 200 Hz − 20 kHz indicate that the FEP layer systems are suitable for applications at least in this range.Piezoelektrische Materialien haben große technische und wirtschaftliche Bedeutung für Anwendungen in Sensoren und Aktuatoren. Neben den traditionellen ferroelektrischen Keramiken und Polymeren bilden Ferroelektrete eine neue Gruppe der Piezoelektrika. Ferroelektrete sind reversible funktionelle Polymersysteme zur Umwandlung von elektrischer in mechanische Energie und umgekehrt. Sie zeichnen sich aus durch eine elastische zelluläre Struktur mit internen quasi-permanenten Dipolen. Der Mechanismus der Piezoelektrizität in Ferroelektreten wird dominiert von der Änderung der einzelnen Dipolmomente bei Einwirkung einer äußeren mechanischen Kraft. Insbesondere zelluläres Polypropylene (PP) war in den vergangenen zwei Jahrzehnten Gegenstand intensiver Forschung und Entwicklung im Hinblick auf die grundlegenden Eigenschaften und Anwendungen von Ferroelektreten. Einige bereits erhältliche kommerzielle Produkte nutzen die in geladenem zellulären PP erreichbaren hohen piezoelektrischen d33-Koeffizienten von 600 pC/N und mehr, sind aber durch eine relativ geringe maximale Betriebstemperatur von ungefähr 60 °C eingeschränkt. Die kürzlich entwickelten Ferroelektrete aus zellulärem Polyethylenterephthalat (PET) und zellulären Cyclo-Olefin-Copolymeren (COC) zeigen eine bessere Temperaturbeständigkeit (vor allem COC), allerdings gewöhlich auf Kosten von geringeren d33-Koeffizienten. Das Ziel der vorliegenden Arbeit ist es, temperaturbeständige Ferroelektrete mit für den Markt geeigneten piezoelektrischen Eigenschaften zu entwickeln. Physikalisches Schäumen ist eine beliebte Methode, um besonders reine Polymerschäume herzustellen. Häufig werden, wegen ihrer guten Löslichkeit in vielen Polymeren, Kohlenstoffdioxid (CO2) und Stickstoff (N2) im superkritischen Zustand als Treibmittel eingesetzt. Der Polyester Polyethylennaphtalat (PEN) hat ähnliche Eigenschaften wie PET, ist jedoch temperaturbeständiger. Ein Dreistufenprozess (Schäumen, Aufblähen und Strecken) wurde entwickelt, um PEN-Schäume für hochwertige Ferroelektrete herzustellen. Ungeschäumte PEN-Folien werden mit superkritischem CO2 unter hohem Druck gesättigt und anschließend unter geringem Druck bei Temperaturen nahe der Glastemperatur geschäumt. Um die Hohlräume zu vergrößern, wird der Schaum anschließend mittels Gasdiffusionsexpansion (GDE) aufgebläht. Nach zusätzlichem biaxialen Verstrecken erhält man die optimalen linsenförmigen Zellen, welche zu einer minimalen mechanischen Steifigkeit und einem maximalen piezoelektrischen d33-Koeffizienten des Ferroelektrets führen. Sowohl Korona- als auch Kontaktaufladung werden an zellulärem PEN erfolgreich eingesetzt. Die Lichtemission der dielektrisch behinderten Entladungen (DBDs) kann klar beobachtet werden. Korona-Aufladung in Gasen mit hohen dielektrischen Durchbruchsfestigkeiten, wie z.B. Schwefelhexafluorid (SF6), ermöglicht es, das Paschen-Durchbruchsfeld in den Hohlräumen und damit die erzielbare interne Ladungsdichte zu erhöhen. Dadurch können für zelluläres PEN piezoelektrische d33-Koeffizienten bis zu 500 pC/N erzielt werden. Piezoelektrischen Resonanzmessungen der Ferroelektrete liefern Steifigkeiten c33 im Bereich von 1 – 12 MPa, Antiresonanzfrequenzen von 0.2 – 0.8 MHz und elektromechanische Kopplungsfaktoren zwischen 0.016 und 0.069. PEN-Ferroelektrete zeigen eine bessere Temperaturstabilität als solche aus PP und PET. Der Anwendungsbereich von unbehandeltem PEN reicht bis etwa 80 – 100°C, jener von getemperten oder bei 120°C geladenen Proben bis etwa 110 – 120 °C. Akustische Messungen im Frequenzbereich von 2 Hz – 20 kHz zeigen die Eignung von PEN-Ferroelektretwandlern für Luftschallanwendungen. Fluoriertes Ethylen-Propylen (FEP) ist ein Fluorpolymer mit sehr guten physikalischen, chemischen und elektrischen Eigenschaften. Die Ladungsspeichereigenschaften von ungeschäumtem FEP können durch die Beimengung von Bornitrid deutlich verbessert werden. In dieser Arbeit wird zelluläres FEP mittels eines einstufigen Prozesses, dem schon erwähnten Schäumen mit überkritischem CO2, hergestellt. Die geladenen FEP-Proben weisen d33-Koeffizienten von bis zu 40 pC/N auf. Ermüdungstests zeigen eine sehr gute mechanische Stabilität von PEN- und FEP-Ferroelektreten. Zelluläre Polymerferroelektrete haben großes Potenzial für Anwendungen, und die Suche nach geeigneten zellulären Morphologien ist eng verknüpft mit dem technischen Aufwand ihrer Herstellung. Alternativ wurden Ferroelektrete mit Sandwich-Strukturen aus FEP-Folien entwickelt. Durch Laserverschmelzen eines FEP-Foliengitters mit zwei umgebenden FEP-Folien wird eine definierte, einheitliche zelluläre Struktur gebildet. Aus dielektrischen Resonanzspektren können effektive piezoelektrische d33-Koeffizienten bis zu 350 pC/N, effektive mechanische Steifigkeiten um 0.3 MPa, Antiresonanzfrequenzen um 30 kHz und elektromechanische Kopplungsfaktoren von etwa 0.05 abgeleitet werden. Proben, welche bei erhöhter Temperatur geladen werden, zeigen höhere Ladungsstabilitäten. Nach geeigneter Aufladung bei 140 °C kann die Arbeitstemperatur bis auf 110 – 120 °C gesteigert werden. Akustische Messungen im Frequenzbereich von 2 Hz – 20 kHz zeigen die Eignung von FEP-Sandwich-Strukturen für Luftschallanwendungen.
41
Yao, Mengmeng. "Determining Polymer Blend Surface Concentration Using Surface Layer Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (SL-MALDI-TOF MS)." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1407941345.
42
Zhu, Geyunjian. "FABRICATION OF SLIPPERY LIQUID-INFUSED POROUS SURFACES USING LAYER-BY-LAYER ASSEMBLY: TOWARDS MULTIFUNCTIONAL SURFACES AND FACILE FABRICATION PROCESSES." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1518051453328934.
43
Choi, Ikjun. "Interfacial assembly of star-shaped polymers for organized ultrathin films." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50246.
Анотація:
Surface-assisted directed assembly allows ultrasoft and replusive functional polymeric “colloids” to assemble into the organized supramolecular ultrathin films on a monomolecular level. This study aims at achieving a fundamental understanding of molecular morphology and responsive behavior of major classes of branched star-shaped polymers (star amphiphilic block copolymers and star polyelectrolytes) and their aggregation into precisely engineered functional ultrathin nanofilms. Thus, we focus on elucidating the role of molecular architecture, chemical composition, and intra/intermolecular interactions on the assembly behavior of highly-branched entities under variable environmental and confined interfacial conditions.
The inherent molecular complexity of branched architectures facilitates rich molecular conformations and phase states from the combination of responsive dynamics of flexible polymer chains (amphiphilic, ionizable arms, multiple segments, and free chain ends) and extened molecular design parameters (number of arms, arm length, and segment composition/sequence). These marcromolecular building components can be affected by external conditions (pH, salinity, solvent polarity, concentration, surface pressure, and substrate nature) and transformed into a variety of complex nanostructures, such as two-dimensional circular micelles, core/shell unimicelles, nanogel particles, pancake & brush micelles, Janus-like nanoparticles, and highly nanoporous fractal networks. The fine balance between repulsive mulitarm interactions and surface energetic effects in the various confined surfaces and interfaces enables the ability to fabricate and tailor well-organized ultrathin nanofilms. The most critical findings in this study include: (1) densely packed circular unimicelle monolayers from amphiphilic and amphoteric multiblock stars controlled by arm number, end blocks, and pH/pressure induced aggregation, (2) monolayer polymer-metal nanocomposites by in-situ nanoparticle growth at confined interfaces, (3) on-demand control of exponentially or linearly grown heterogeneous stratified multilayers from self-diffusive pH-sensitive star polyelectrolyte nanogels, (4) core/shell umimicelle based microcapsules with a fractal nanoporous multidomain shell morphology, and (5) preferential binding and ordering of Janus-like unimicelles on chemically heterogeneous graphene oxide surfaces for biphasic hybrid assembly.
The advanced branched molecular design coupled with stimuli responsive conformational and compositional behavior presents an opportunity to control the lateral diffusion and phase segregation of branched compact supermolecules on the surface resulting in the generation of well-controllable monolayers with tunable ordering and complex morphology, as well as to tailor their stratified layered nanostructures with switchable morphological heterogeneity and multicompartmental architectures. These surface-driven star polymer supramolecular assemblies and interfaces will enable the design of multifunctional nanofilms as hierarchical responsive polymer materials.
44
Tomaino, Andrew R. "Layer-by-Layer Assemblies for Membrane-Based Enzymatic Catalysis." UKnowledge, 2014. http://uknowledge.uky.edu/cme_etds/38.
Анотація:
While considerable progress has been made towards understanding the effect that membrane-based layer-by-layer (LbL) immobilizations have on the activity and stability of enzymatic catalysis, detailed work is required in order to fundamentally quantify and optimize the functionalization and operating conditions that define these properties. This work aims to probe deeper into the nature of transport mechanisms by use of pressure-induced, flow-driven enzymatic catalysis of LbL-functionalized hydrophilized poly(vinyldiene) (PVDF)-poly(acrylic acid) (PAA)-poly(allylamine hydrochloride) (PAH)-glucose oxidase (GOx) membranes. These membranes were coupled in a sealed series following cellulose acetate (CA) membranes for the elimination of product accumulation within the feed-side solution during operation. At pH = 6 and T = 21oC, the enzymatic catalysis of LbL-immobilized GOx from Aspergillus niger performed remarkably well in comparison to the homogeneous-phase catalysis within an analogous aqueous solution. On average, the enzymatic turnover was 0.0123 and 0.0076 mmol/(mg-GOx)(min) for the homogeneous-phase catalysis and the LbL-immobilized catalysis, respectively. Multiple consecutive permeations resulted in replicable observed kinetic results with R2 > 0.95. Permeations taking place over the course of a three week trial period resulted in a retention of >90% normalized activity when membranes were removed when not in use and stored at -20oC, whereas the homogenous-phase kinetics dropped below 90% normalized activity in under one day.
45
Sieczkowska, Barbara. "Functional polymer layers with protected amines." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244668077080-12212.
Анотація:
This work refers to the area of bio-nanotechnology and concerns the selective immobilization of DNA or other bio-template on microstructured gold contacts and which then permit a coordinated cooperation of several of these nanotemplate, e.g., within a microreactor. The immobilization of such nano-objects should be realized through functional thin polymer films which provide binding groups. Thus, the main aim of this work was the development of polymeric materials for thin functional films which permit to deposit on different substrates a wide variation of functional elements or metal structures and to achieve a pattern formation using optical grid methods. In order to realize this concept it was necessary to design and develop a polymer system based on suitable photolabile units and in addition having anchoring groups which attach on specific substrates like gold. In this terpolymer concept was aimed for which consists of three components with particular functions in suitable molar ratios, which allow the tune the properties of the materials, and provide: amino photolabile protected groups for the photolithographic creation of patterned areas with free amino groups, which are available for further modifications like attachment of colloids, metallization or attachment of DNA strands; disulfide derivative anchor groups providing anchoring capacity for gold surface and spacer groups for adjusting the film quality. These multifunctional terpolymers should be synthesised by free radical polymerisation of suitable monomers. Although these techniques are successful, they are limited by their complexity, rigorous synthetic demands, as well as incompatibility with many functional termolabile and highly reactive functionalities. To overcome these difficulties a polymerisation technique based on “living” free radical polymerisation has been used in this work. A highly efficient polymer-analogous modification allows to introduce the functionalities after the polymer construction reaction. The production of suitable prepolymers [poly(styrene-r-4-propargyl-oxystyrene)] was carried out with the help of a controlled synthesis methodology “nitroxide mediate radical polymerization" followed by polymer analogous reaction using one of the most efficient click reactions, the Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition between terminal acetylenes and azides to attach further functionalities through the formation of a stable 1,4-disubstituted 1,2,3-triazol ring . The combination of nitroxide mediated radical polymerization (NMRP) and click chemistry was used to produce well-defined random copolymer. It could already be shown that also block copolymers can be prepared which give the chance to combine nanostructure formation in block copolymers with special functionality. Thus, the special properties of these functional polymers like the capability for photopatterning and anchoring onto gold substrates make them very interesting for nanotechnology applicationsDiese Arbeit bezieht sich auf das Gebiet der Bionanotechnologie und betrifft ein neuartiges Verfahren zur selektiven Immobilisierung der DNA oder anderer Biomoleküle auf mikrostrukturierten Goldkontakten, welche dann ein koordiniertes Zusammenwirken von einzelnen Nanomolekülen ermöglichen, z.B. in einem Mikroreaktor. Die Immobilisierung solcher Nanoobjekte soll durch dünne Funktionsschichten realisiert werden, die die Anbindungsgruppen liefern. Folglich war das Hauptziel dieser Arbeit die Entwicklung von Polymermaterialien für dünne Funktionsschichten, die die Aufbringung einer großen Vielzahl von Funktionselementen oder metallischen Strukturen auf verschiedenen Substraten gestatten und die Strukturierung durch den Einsatz von lithographischen Methoden ermöglichen. Um dieses Konzept zu realisieren, war es notwendig, ein Polymersystem zu gestalten und zu entwickeln, welches auf geeignete photolabile Einheiten basiert und zusätzlich Ankergruppen hat, die mit spezifischen Substraten wie Gold verbunden ist. Dieses Terpolymerkonzept wurde gezielt aus drei Komponenten mit speziellen Funktionen in entsprechenden molaren Verhältnissen gebildet, die eine Abstimmung der Materialeigenschaften ermöglicht und folgendes bereitstellt: photolabile geschützte Aminogruppen für die photolitographische Strukturerzeugung mit freien Aminogruppen, welche für weitere Modifikationen verfügbar sind wie das Anhängen von Kolloiden, die Metallisierung oder Anfügung von DNA-Strängen; disulfide Derivate für die kovalente Anbindung auf der Goldoberfläche und Spacer-Gruppe für Verbesserung der Schichtenbildung. Diese multifunktionalen Terpolymere sollen durch eine freie radikalische Polymerisation von entsprechenden Monomeren synthetisiert werden. Obwohl diese Techniken erfolgreich sind, sind sie eingeschränkt durch ihre Komplexität, den strengen synthetischen Anforderungen, sowie der Inkompatibilität mit vielen funktionalen thermolabilen und hochreaktiven Funktionalitäten. Um diese Schwierigkeiten zu überwinden wurde eine Polymerisationstechnik für diese Arbeit genutzt, die auf der „lebenden“ freien radikalischen Polymerisation basiert. Eine hoch effiziente polymeranaloge Modifizierung erlaubt die Einführung von Funktionalitäten nach der Polymeraufbaureaktion. Die Herstellung von entsprechenden Präpolymeren Poly(Styrol-r-4-Propargyl-oxystyrol) wurde mittels einer kontrollierten Synthesemethodik „Nitroxid-mediated controled radical polymerisation“ (NMRP) durchgeführt, gefolgt von der Polymeranalogreaktion, die eine der effizientesten Click-Reaktion - die Cu(I) katalysierte 1,3-dipolar Cycloaddition von terminalen Alkinen an Aziden nach Huisgen nutzt, um weiter Funktionalitäten durch die Bildung eines stabilen 1,4-disubstituierten-[1,2,3]-Triazolringes anzufügen. Die Kombination von NMRP und Click-Chemie wurde zur Herstellung eines exakt definierten Random Copolymers genutzt. Es konnte bereits gezeigt werden, dass auch Blockcopolymere geschaffen werden können, die eine Möglichkeit zur Kombination von Nanostrukturformationen in Blockcopolymeren mit speziellen Funktionaltäten bieten. Folglich sind die speziellen Eigenschaften dieser Funktionalpolymere wie die Fähigkeit zur Photostrukturierung und Verankerung auf Goldsubstraten für nanotechnologische Anwendungen sehr interessant
46
Wahab, Md Saidin. "Selective laser sintering of polymer nanocomposites." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496208.
47
Perrin, Éric. "Contribution a l'interpretation des proprietes vibrationnelles du polyacetylene et de certains polymeres conjugues." Nantes, 1988. http://www.theses.fr/1988NANT2007.
Анотація:
Etude vibrationnelle experimentale et theorique de plusieurs polymeres conducteurs. Les resultats obtenus sur du polyacetylene oriente confirment le modele de distribution bimodale de segments conjugues. Etude de l'effet de conjugaison sur le polyacetylene pur et dope (fecl::(4)**(-)) et sur le polyphenylene-vinylene
48
Suntivich, Rattanon. "Inkjet-assisted printing of encapsulated polymer/biopolymer arrays." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52300.
Анотація:
The goal of the proposed study is to understand the morphology, physical, and responsive properties of synthetic polymer and biopolymer layer-by-layer (LbL) arrays using the inkjet printing and stamping technique, in order to develop patterned encapsulated thin films for controlled release and biosensor applications. In this study, we propose facile fabrication processes of hydrogen-bonded and electrostatic LbL microscopic dot arrays with encapsulated target organic and cell compounds. We study encapsulation with the controllable release and diffusion properties ofpoly(vinylpyrrolidone) (PVPON), poly(methacrylic acid) (PMAA), silk-polylysine, silk-polyglutamic acid, pure silk films, and E-coli cells from the multi-printing process. Specifically, we investigate the effect of thickness, the number of bilayers, and the hydrophobicity of substrates on the properties of inkjet/stamping multilayer films such as structural stability, responsiveness, encapsulation efficiency, and biosensing properties.
We suggest that a more thorough understanding of the LbL assembly using inkjet printing and stamping techniques can lead to the development of encapsulation technology with no limitations on either the concentration of loading, or the chemical and physical properties of the encapsulated materials. In addition, this study offers new encapsulation concepts with simple, cost effective, highly scalable, living cell-friendly, and controllable patterning properties.
49
Zhang, Hailiang. "Wavelength Tunable Devices Based on Holographic Polymer Dispersed Liquid Crystals." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1203610126.
50
Park, June Hyoung. "Charge transport in organic multi-layer devices under electric and optical fields." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1182273300.