Dissertations / Theses on the topic 'Hydrophobic materials'

Porous silicon (Psi) and nanocellulose (NC) hydrogels are nanostructured materials with several properties that make them promising for drug delivery applications. In this work, β-carotene (BC) and clofazimine (CFZ) are used as model molecules to investigate the physical and chemical processes governing the interactions of hydrophobic molecules with both inorganic (Psi) and organic (NC) nanostructured carriers. Despite the large number of advantages, Psi does not perform well as carrier for BC, since it stimulates the molecule degradation even if its surface is carefully passivated. Furthermore, during the release experiments, BC tends to nucleate on Psi surface forming aggregates whose dissolution is much slower than the BC molecules release, thus they negatively impact on the control over the drug release. On the other hand NC hydrogels do not pose heavy issues to the release of lipophilic drugs, provided that a suitable surfactant (either Tween-20 or Tween-80) mediates the molecule solvation and its subsequent release into aqueous media. Moreover, NC gels protect BC from degradation much better than its storage in freezer or in organic solvent, making these carriers interesting for DD.

Porous silicon (Psi) and nanocellulose (NC) hydrogels are nanostructured materials with several properties that make them promising for drug delivery applications. In this work, β-carotene (BC) and clofazimine (CFZ) are used as model molecules to investigate the physical and chemical processes governing the interactions of hydrophobic molecules with both inorganic (Psi) and organic (NC) nanostructured carriers. Despite the large number of advantages, Psi does not perform well as carrier for BC, since it stimulates the molecule degradation even if its surface is carefully passivated. Furthermore, during the release experiments, BC tends to nucleate on Psi surface forming aggregates whose dissolution is much slower than the BC molecules release, thus they negatively impact on the control over the drug release. On the other hand NC hydrogels do not pose heavy issues to the release of lipophilic drugs, provided that a suitable surfactant (either Tween-20 or Tween-80) mediates the molecule solvation and its subsequent release into aqueous media. Moreover, NC gels protect BC from degradation much better than its storage in freezer or in organic solvent, making these carriers interesting for DD.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 18).
This project aims to create a hydrophobic surface through a top down fabrication process of a nanostructure surface on a glass surface. The nanostructure is created through reactive ion etching utilizing silver as a mask. The silver mask is the result of a solid state thermal dewetting process which is controlled by varying the temperature and time of the process. Using this fabrication process, contact angles up to 137 degrees was achieved. Further surface modification resulted in contact angles exceeding 150 degrees. Superhydrophobic surfaces were made with the addition of a secondary roughness feature and the a PDMS coating.
by Michelle Chao.
S.B.

Densification and submergence of floating crude oil is proposed as a novel oil spills treatment method. Surface application of dry granular materials (e.g., quartz sand, limestone) on top of a floating oil layer increases the density of the floating oil phase/granule mixture and leads to formation of relatively large and stable aggregates with significant amounts of captured oil. The aggregates separate from the floating hydrophobic phase and settle by gravity. Implementation of this method will reduce the impact radius of a spill and its mobility, preventing direct contamination of beaches, coastal flora and fauna. The major objective of this research was to examine interactions of particles with hydrophobic liquid-water interface from different perspectives. The important characteristics of the process, such as oil removal efficiencies, optimal particle-to-oil ratios and particle size ranges, were experimentally defined. A series of experiments was conducted to investigate aggregation and dissolution rate constants of the submerged hydrophobic liquids in salt water and deionized water, and to study the impact of the surface porosity of the granular particles on oil capture efficiencies. In addition to crude oil (South Louisiana crude, MC 252), aggregation volumes of quartz sand with other hydrophobic liquids (alkanes and aromatics) were analyzed in relation to wetting characteristics and physical properties of the liquids. A classification of the main types of oil-particle aggregates was developed based on the formation characteristics of the aggregates. Moreover, under specific conditions, depending on the application rates of the granular materials, unique interactions of the particles with the hydrophobic liquid-water interface were observed and defined (bowl formation and roping). These concepts can be utilized to control surface mobility of floating oils, especially during the initial stages of an oil spill, while the oil layer is intact, and when other treatment methods may not be suitable near coastal areas, where transport of floating oils can significantly impact coastal ecosystems.

For a broad class of two-dimensional (2D) materials, the transition from isotropic fluid to crystalline solid is described by the theory of melting due to Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY). According to this theory, long-range order is achieved via elimination of the topological defects which proliferate in the fluid phase. However, many natural and man-made 2D systems posses spatial curvature and/or non-trivial topology, which require the presence of topological defects, even at T=0. In principle, the presence of these defects could profoundly affect the phase behavior of such a system. In this thesis, we develop and characterize an experimental system of charged colloidal particles that bind electrostatically to the interface between an oil and an aqueous phase. Depending on how we prepare the sample, this fluid interface may be flat, spherical, or have a more complicated geometry. Focusing on the cases where the interface is flat or spherical, we measure the interactions between the particles, and probe various aspects of their phase behavior. On flat interfaces, this phase behavior is well-described by KTHNY theory. In spherical geometries, however, we observe spatial structures and inhomogeneous dynamics that cannot be captured by the measures traditionally used to describe flat-space phase behavior. We show that, in the spherical system, ordering is achieved by a novel mechanism: sequestration of topological defects into freely-terminating grain boundaries (“scars”), and simultaneous spatial organization of the scars themselves on the vertices of an icosahedron. The emergence of icosahedral order coincides with the localization of mobility into isolated “lakes” of fluid or glassy particles, situated at the icosahedron vertices. These lakes are embedded in a rigid, connected “continent” of locally crystalline particles.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references.
Micrometer- and nanometer-scale chemical patterns are indispensable and ubiquitous in a range of applications, such as optoelectronic devices and (bio) chemical sensors. This thesis studies chemical surface patterning utilizing polyelectrolyte multilayers for electronic and biological applications. It focuses on both fundamental study and application development in the field of layer-by-layer self-assembled composite thin films, with the goal of defining new concepts allowing for technological breakthrough. In the process of completing it, a multicomponent patterning technology that has been a bottleneck in realizing practical devices utilizing the multilayers has been developed. To achieve this goal, a multilayer transfer printing concept was applied to serial printing of individual device components. The main achievements include fundamental studies about uniform multilayer assembly of charged macromolecules on neutral hydrophobic surfaces as the principle of the technique, and the demonstration of multicomponent patterning of polyelectrolyte/nanoparticle composite thin films on a flexible substrate.
(cont.) Extending the technique toward nanometer-scale patterning, a new polymeric mold material that was suitable for sub-100 nm structuring was studied and used for chemical patterning for flow control in microfuidic devices and nanoparticle assembly for potential biological applications, combined with polyelectrolyte multilayers.
by Juhyun Park.
Ph.D.

In this thesis, we focused on the understanding of the synthesis and texturization processes of hydrophobic and (super)hydrophobic fluorinated surfaces by atmospheric plasmas.

First, we focused on the surface modifications of a model surface, the polytetrafluoroethylene (PTFE), by the post-discharge of a radio-frequency plasma torch. The post-discharge used for the surface treatment was characterized by optical emission spectroscopy (OES) and mass spectrometry (MS) as a function of the gap (torch-sample distance), and the helium and oxygen flow rates. Mechanisms explaining the production and the consumption of the identified species (N2, N2+, He, O, OH, O2m, O2+, Hem) were proposed.

The surface treatment was then investigated as a function of the kinematic parameters (from the motion robot connected to the plasma torch) and the gas flow rates. Although no change in the surface composition was recorded, oxygen is required to increase the hydrophobicity of the PTFE by increasing its roughness, while a pure helium plasma leads to a smoothing of the surface. Based on complementary experiments focused on mass losses, wettability and topography measurements coupled to the detection of fluorinated species on an aluminium foil by XPS, we highlighted an anisotropic etching oriented vertically in depth as a function of the number of scans (associated to the treatment time). Atomic oxygen is assumed to be the species responsible for the preferential etching of the amorphous phase leading to the rough surface, while the highly energetic helium metastables and/or VUV are supposed to induce the higher mass loss recorded in a pure helium plasma.

The second part of this thesis was dedicated to the deposition and the texturization of fluorinated coatings in the dielectric barrier discharge (DBD). The effects of the nature of the precursor (C6F12 and C6F14), the nature of the carrier gas (argon and helium), the plasma power, and the precursor flow rate were investigated in terms of chemical composition, wettability, topography and crystallinity by SIMS, XPS, WCA, AFM and XRD. We showed that hydrophobic surfaces with water contact angles (WCA) higher than 115° were obtained only in the presence of argon and were assumed to be due to the roughness created by the micro-discharges. Plasma-polymerized films in helium were smooth and no WCA higher than 115° was observed. We also studied the impact of the deposition rate and the layer thickness in the hydrophobic properties as well as the polymerization processes through the gas phase characterization.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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.

Proton exchange membrane fuels cells (PEMFCs) are one of the primary alternatives to internal combustion engines. The key component is the proton exchange membrane, or PEM, which should meet a number of requirements, including good proton conductivity under partially humidified conditions. A number of alternative PEMs have been synthesized by copolymerizing various aromatic comonomers, but the smaller ion channels prohibit rapid proton transport under partially hydrated conditions. One solution has been to synthesize multiblock copolymers from hydrophilic and hydrophobic oligomers to ensure sufficient ion channel size. Four multiblock systems were synthesized from hydrophobic and hydrophilic oligomers and were characterized in this thesis. The first multiblock system incorporated a partially fluorinated monomer into the hydrophobic block, to improve phase separation and performance under partially humidified conditions. The second study was focused on phase separation and structure-property relationships as a function of casting conditions of a biphenol-based multiblock series. The third study featured a novel hydroquinone-based hydrophilic oligomer in the multiblock copolymer, which showed the promise of a higher ionic density, degree of phase separation and proton conductivity values. The fourth study in this thesis entailed the comparison of a block copolymer produced with two distinct synthetic routes: the multiblock synthesis from separate oligomers as previously published in the literature, and a segmented route seeking to achieve comparable structure-property relationships with the same monomers, but using a simpler synthetic route. The two block copolymer series were found to be comparable in their structure-property relationships.
Master of Science

Amyotrophic lateral sclerosis (ALS) is a devastating disease. Currently, there is no cure for this disease, and effective treatment strategies are greatly needed. Calpain activation plays a major role in the motor neuron degeneration that causes ALS. Therefore, therapeutic strategies can inhibit calpain activity in the central nervous system (CNS) have great clinical potential. The calpain inhibitors AK295 and MDL-28170 have been demonstrated to be neuroprotective in animal models of neurological injury, and should have great potential to treat ALS; however delivery problems have hindered their clinical success. Therefore, development of a new strategy that can locally deliver the calpain inhibitors to the central nervous system could significantly improve the treatment of ALS. The objectives of my thesis research were (1) to develop high molecular weight polyketals that provide sustained release properties for hydrophobic molecules, (2) to formulate calpain inhibitor-encapsulated polyketal microparticles which have a release half life of one month in vitro, (3) and to evaluate the performance of polyketal microparticles for delivering calpain inhibitors to the spinal cord in vivo. In completing these specific aims, we have developed biodegradable polymeric microparticles for the delivery of calpain inhibitors, AK295 and MDL-28170 to treat ALS. The results of calpain assays showed that both AK-PKMs and MDL-PKMs maintained most of their inhibitory activities even after the robust emulsion process. The in vitro release profile of MDL-28170 in MDL-PKMs showed that 50 % of the drug was released in the first 30 days. Experiments using dye-encapsulated microparticles showed that polyketal microparticles (1-2 ìm) are not easily cleared in the neutral physiological environment and can have potential to continuously release drug from the injection sites in the spinal cord. The efficacy of calpain inhibitor-encapsulated PKMs were studied by evaluation the behavior and survival of SOD1G93A rats, a genetic rat model for ALS. We observed the trend toward improvements in grip strength and rotarod performance in the first two months from the AK-PKMs treated group, however, further improvements are needed to enhance their in vivo efficacy.

Condensation of water vapor is an everyday phenomenon which plays an important role in power generation schemes, desalination applications and high-heat flux cooling of power electronic devices. Continuous dropwise condensation is a desirable mode of condensation in which small, highly-spherical droplets regularly form and shed off the surface before a thick liquid is formed, thereby minimizing the thermal resistance to heat transfer across the condensate layer. While difficult to induce and sustain, dropwise condensation has been shown to achieve heat and mass transfer coefficients over an order of magnitude higher than its filmwise counterpart. Superhydrophobic surfaces have been extensively studied to promote dropwise condensation with mixed results; often surfaces that are superhydrophobic to deposited droplets formed in the gas phase above the surface do not retain this behavior with condensed droplets nucleated and grown on the surface. Recently, nanostructured superhydrophobic surfaces have been developed that are robust to vapor condensation; however, these surfaces still are not ideal for condensation heat transfer due to the high thermal resistance of the vapor layer trapped underneath the droplets and the reduced footprint of direct contact between the highly-spherical droplets and the underlying substrate. This work has two main objectives. First, a comprehensive free energy based thermodynamic model is developed to better understand why traditional superhydrophobic surfaces often lose their properties when exposed to condensed droplets. The model is first validated using data from the existing literature and then extended to analyze the suitability of amphiphilic (e.g. part hydrophobic and part hydrophilic) nanostructured surfaces for condensation applications. Secondly, one of the promising amphiphilic surfaces identified by the thermodynamic model is fabricated and tested to observe condensation dynamic behavior. Two complementary visualization techniques, environmental scanning electron microscopy (ESEM) and optical (light) microscopy, are used to probe the condensation behavior and compare the performance to that of a traditional superhydrophobic surface. Observations from the condensation experiments are used to propose a new mechanism of coalescence that governs the temporal droplet size distribution on the amphiphilic nanostructured surface and continually generates fresh sites for the droplet nucleation and growth cycle that is most efficient at heat transfer.

It was the objective of this project to provide a glass cleaner formulation for a wet wipe application with cleaning and anti-fogging properties. This glass cleaner formulation was developed for automotive glass i.e. interior of windscreens. This formulation relates to a glass cleaner with a composition comprising of: (a) a blend of amphoteric surfactants; (b) a solvent system with a combination of glycol ethers; and (c) an aqueous solvent system. This glass formulation must provide good cleaning properties while also providing good wetting and sheeting properties to assist with anti-fogging properties. The objectives were obtained using 2 specific approaches: The first was by using a blend of 2 amphoteric surfactants in an alkaline medium, allowing the glass surface to become more hydrophilic which will also assist with reduction of surface tension on the glass surface. The second was by using the glycol ethers that have good coupling properties and surface tension reducing properties. The formulation was evaluated using commercial standard test methods as per the industry. A predictive model was successfully obtained for each of the five criteria that were evaluated using the 25 formulations derived from the statistical design. There were variables and variable interactions that were antagonistic for some of the criteria which were found to be synergistic for others. To achieve satisfactory cleaning, the fogging rating had to be compromised.

Accidental or deliberate crude oil spills have been, and still continue to be, a significant source of environmental pollution, and pose a serious environmental problem, due to the possibility of air, water and soil contamination. Chlorinated volatile organic compounds (VOCs), such as 1,1-dichloroethylene (DCE) and aromatic hydrocarbons, BTEX (benzene, toluene, ethyl benzene and xylene) constitute a significant fraction of hazardous air and water pollution. Human beings are exposed to elevated levels of a wide spectrum of VOCs, many of which have been found to be toxic and potentially carcinogenic. Removal of these organic contaminants from water and wastewater has been achieved using several treatment technologies, such as advanced oxidation processes, air stripping, reverse osmosis, ultrafiltration and adsorption. Adsorption processes can be successfully used when contaminants are not amenable to fast biological degradation. Permeable Reactive Barriers (PRB) are one of the most promising passive treatment technologies, due to their effectiveness regarding various contaminants, and their low cost compared to other in situ technologies. Typical PRB configuration consists in a permeable treatment zone placed vertically to the flow path of groundwater, which contains reactive material that immobilises or decomposes the contaminants by adsorption as the groundwater flows through it. PRBs are installed as permanent, semi-permanent, or replaceable units. A wide variety of pollutants are degraded, precipitated, sorbed or exchanged in the reactive zone, including chlorinated solvents, heavy metals, radionuclides and other organic and inorganic species. Conventional permeable reactive barriers for the decontamination of water are based on systems which most widely use Granular Activated Carbon (GAC). GAC has been shown to be only slightly effective in treating water containing very soluble compounds, such as oxygenated organics, or low molecular weight compounds, such as DCE and vinyl chloride (VC). However, their use for the removal of organic contaminants in water and wastewater applications can be complicated by the presence of dissolved natural organic matter in the water stream being treated, which can decrease the removal efficiency of GAC. When activated carbon is saturated, it has to be regenerated or renewed, which is rather an expensive operation. The adsorbed molecules are then released and still have to be destroyed by thermal treatments. Moreover, this additional treatment also degrades the activated carbon adsorption properties in the long term [1]. Zero-valent iron (ZVI), which directly degrades several contaminants, appears to be ineffective too, both on irreducible compounds such as DCE and chlorobenzenes as well as on hydrocarbons. Furthermore, when ZVI is used, it causes a reduction in the permeability of the barrier due to encrustations or precipitation of minerals which derive from the reactions between the ions of the oxidised metal and the substances contained in the groundwater [1-2]. Therefore, when operating with a barrier based on metallic iron alone, the chemical reduction reaction of the reducible compounds can require from 1 to 2 days. In this case, it is only the thickness of the iron which can ensure the time necessary for completing the reactions and large quantities are required to guarantee the complete decontamination of the groundwater. Recently, high-silica zeolites were shown to be more effective than activated carbon or ZVI in removing certain organics from water [3-4]. The selection of zeolites from among the large variety of adsorbent materials is based on their stability and efficiency properties. To date, the adsorption mechanisms of zeolites in gas phase systems have been widely investigated. On the contrary, studies and applications on organic pollutants adsorption in microporous zeolitic materials from aqueous media have been relatively scarce. Adsorption from gas phase systems can significantly differ from that observed from the corresponding aqueous solutions, due to the highly polar nature of water molecules. In literature, it has been reported that water plays a very important role in the diffusion of hydrocarbons in the zeolite pore system. In particular, large amounts of co-adsorbed water molecules block the migration of host molecules such as alkanes and olefins, thus reducing the adsorption capacity of zeolites, especially at low adsorbate concentrations. As a consequence, water acts as a screen between the cationic sites of the zeolite and the hydrocarbon molecules (screening effect) and reduces both the sorption volume (steric effect) and the aperture of the zeolite windows (blocking effect). On the contrary, small amounts of co-adsorbed water lower the extent of specific adsorption without significant blocking effects. However, as mentioned above, this research on hydrocarbon adsorption has also mainly been focused on single components from air matrices, whereas there are few studies involving aqueous dilute solutions. Nonetheless, in most environmental applications, these pollutants are present as very dilute aqueous solution mixtures. The work developed in the present thesis is part of a wider project whose purpose is to study the interaction and mobility of groundwater pollutants adsorbed in zeolite pores, in order to improve the efficiency of permeable reactive barriers. This project involves Ferrara and Bologna Universities with the financial support of the ENI and the scientific support of Dr. Roberto Bagatin of the research centre of Novara. Several techniques were employed such as X ray diffraction, gas chromatography, IR spectroscopy, thermal analyses, as well as computational studies. In this thesis, combined diffractometric, thermogravimetric and gas chromatographic techniques were employed to study the adsorption process in order to: 1) investigate the adsorptive properties of these hydrophobic synthetic zeolites; 2) characterise their structure after the adsorption of selected contaminants (1-2 dichloroethane, tert-butyl methyl ether and toluene); 3) localise the organic species in the zeolite channel system; 4) probe the interactions between organic molecules and framework oxygen atoms; 5) compare the adsorption data for a mixture of these contaminants with concentrations in the ppb and ppm range; 6) characterise the kinetic of the adsorption processes. In particular, the thermodynamic and kinetic of the adsorption processes of contaminants on hydrophobic zeolites were obtained by using complementary, batch, linear and non-linear chromatography and thermogravimetry techniques. Batch and non-linear chromatography were mainly used to measure the adsorption isotherms for the compounds of interest. The adsorption isotherm is useful in representing the capacity of a zeolite to adsorb organics from waste, and in providing description of the functional dependence of capacity on the concentration of pollutants. Experimental determination of the isotherm allows to evaluate the feasibility of adsorption for treatment, to select a zeolite, and to estimate adsorbent dosage requirements. Moreover, it is possible to evaluate the adsorption energy distribution of the process from isotherm parameters. Batch and linear chromatography, instead, were employed to investigate the kinetic of the adsorption. Kinetics deals with changes in chemical properties in time and is especially concerned with the rate of changes and plays a fundamental role in determining the proper time contact for the removal of pollutant components from wastewater. In addition, an original theoretical model able to give information regarding the kinetic and the thermodynamic constants of systems in which both reactions and adsorption processes occur simultaneously was developed. To investigate the adsorption mechanism, diffraction techniques were employed to localize the organics adsorbed into the zeolite structure. The information gathered by this latter investigation – in cooperation with the Earth Science Department UNIFE - allows to define the interactions between organic molecules and zeolite framework. Finally, adsorption on mesoporous materials was investigated. It is well known that water is contaminated by different classes of substances, and zeolites are mainly suitable for molecules with dimensions comparable to that of their pores. However, many compounds belonging to the class of emergent contaminants have large molecular dimensions, and in such cases mesoporous materials can be more efficient than zeolites. To accomplish this task MCM-41 and HMS were synthesized and characterised – this work was carried out at the ‘Institut Charles Gerhardt (ICG), Matériaux Avancés pour la Catalyse et la Santé (MACS)’ at Montpellier (France) with the supervision of Prof. Francesco di Renzo and Dr. Anne Galarneau – and then the adsorption of acid perfluorooctanoic onto these mesoporous materials was performed.

La modificació de les superfícies dels materials permet obtenir propietats diferents a les que presenta el substrat prèviament o preservar-lo del medi que l’envolta. Les tècniques emprades amb aquest objectiu són molt variades donat que la ciència de materials fa dècades que investiga en la millora dels materials existents. La present tesi es centra en el tractament de quatre metalls i aliatges diferents modificats superficialment per tal de convertir-se en sistemes superhidrofòbics. Els metalls seleccionats són el coure i l’alumini purs, UNS C10100 i AA1070, respectivament, que tenen com aplicació destacada les conduccions elèctriques per la seva extraordinària conductivitat. Evitar que l’aigua pugui entrar en contacte amb aquets metalls reduint la seva degradació incrementarà la vida útil. I com aliatges, els acers inoxidables més àmpliament utilitzats com són AISI 316L i AISI 304 per les bones propietats mecàniques que presenten i la seva resistència davant la corrosió. L’aigua i temperatures altes són condicions excel·lents per la proliferació de molts bacteris, evitar que en materials utilitzats en la indústria alimentària i farmacèutica, com són aquests acers inoxidables, puguin desenvolupar-se bacteris i algues, és el principal motiu per haver estat seleccionats en aquest estudi. La superhidrofobicitat és una característica superficial present en alguns animals i plantes de forma natural, on es redueix el contacte amb l’aigua, donat que es formen gotes amb angle de contacte amb la superfície superiors a 150°. Aquest fet és conseqüència de la particular rugositat que presenten i la baixa tensió superficial. L’exemple icònic d’aquesta propietat és la flor de Lotus, considerada com a símbol de puresa en moltes cultures degut a la seva manca de mullabilitat en aigua i a l’efecte d’autoneteja que presenten els pètals. Aquest efecte està associat a l’aïllament de l’aigua, donat que davant de la presència de brutícia, les gotes d’aigua que es dipositen en la superfície per la pluja, llisquen per ella i expulsen les partícules alienes, aquesta propietat permet la seva aplicació en entorns on la neteja sigui dificultosa o sigui determinant el manteniment de la superfície en condicions intactes. Altres propietats associades a la superhidrofobicitat són l’antiadhesió, donat que l’aigua no interacciona amb la superfície i, a més, la brutícia tendeix a barrejar-se amb l’aigua i a no dipositar-se en el material, autoneteja, així com la separació de components líquids de diferents polaritat que té moltes aplicacions en l’aïllament de contaminants orgànics en fase líquida. L’obtenció de superfícies artificials superhidrofòbiques s’anomena mimetització de la Natura, i són múltiples els estudis que s’esforcen en els darrers anys en obtenir materials amb aquestes prestacions i que la durabilitat d’aquesta propietat estigui garantida, ambdues estratègies s’han també estudiat en aquesta tesi. L’obtenció de la superhidrofobicitat en metalls requereix de dues premisses que han de complir-se simultàniament: una baixa tensió superficial i una rugositat superficial jerarquitzada del substrat, on coexisteixen una morfologia micromètrica i nanomètrica minimitzant el contacte entre l’aigua i la superfície del material, contribuint a l’aïllament d’aquest. Donada l’elevada tensió superficial que caracteritza als metalls, és necessari l’addició de components com els àcids grassos o els flurosilans que al dipositar-se en la superfície actuen com a reductors de la tensió superficial. En aquest estudi ens hem decantat per treballar amb espècies que siguin mediambientalment respectuoses, per aquest motiu s’ha descartat l’ús de fluorosilans i derivats. Per garantir l’obtenció d’aquests materials a nivell industrial, aquest treball s’ha caracteritzat per optimitzar els temps de fabricació i simplificat la tecnologia emprada per garantir una elevada competitivitat. A diferència dels estudis consultats, no només s’ha caracteritzat la morfologia i rugositat de la superfície obtinguda sinó que la investigació s’ha centrat en identificar el mecanisme de creixement del revestiment i les reaccions que hi tenen lloc, per tal de conèixer totes les variables del procés, l’evolució de les estructures formades amb el temps de reacció i la seva influència en l’obtenció del producte final, donat que les aplicacions del material final estan determinades per les característiques de la capa generada. Totes aquestes característiques s’han desenvolupat en el present treball pels quatre substrats seleccionats. En el cas de l’alumini (UNS AA1070), la rugositat micromètrica generada en la superfície ha comportat l’eliminació de l’alúmina natural i la formació de terrasses micromètriques amb forats que propicien que l’aire quedi atrapat i eviti el contacte superfície-aigua, mitjançant un procés d’immersió en una dissolució de 30 g d’àcid lauric per litre de dissolució 30:70 d’àcid clorhídric i etanol. S’han succeït una sèrie de reaccions entre els productes i la superfície, on finalment s’ha produït el dipòsit de compostos de laureat d’alumini i alúmina que presenten un creixement horitzontal (paral·lel a la superfície del substrat) i en vertical (perpendicular a la superfície del substrat) fins a l’obtenció d’una superfície superhidrofòbica amb angles de contacte superior als 150°. Aquest mecanisme de creixement s’anomena model 2D de Stransky-Krastanov. Per tal de millorar la resistència a la corrosió d’aquest substrat d’alumini, també s’ha investigat un procediment similar a l’anterior, afegint una etapa d’anoditzat a la superfície, previ a la immersió en àcid lauric, obtenint resultats positius en superhidrofobicitat i una marcada millora en el potencial de corrosió en medi salins. En aquest cas, la influència de la capa d’anoditzat en el mecanisme de creixement és molt elevada i a temps superiors als 60 minuts, es genera una morfologia porosa i hexagonal similar a la que presenten els ruscs d’abelles, on els productes de reacció entre l’alúmina, l’alumini substrat i l’àcid lauric ressegueixen l’estructura prèviament formada en l’etapa d’anoditzat. En aquest tipus de materials s’ha estudiat l’estabilitat de la superhidrofobicitat en condicions d’extrema baixa temperatura, treballant amb nitrogen líquid, i ha permès concloure que les superfícies d’alumini anoditzades i tractades amb àcid lauric, eviten una bona adhesió del gel i, a més, la propietat de superhidrofobicitat es manté intacte al tornar a condicions normals de temperatura i humitat. Els aliatges d’acer inoxidable i el coure no han respost positivament al mateix procediment aplicat en l’alumini, i ha estat necessari buscar altra metodologia per l’obtenció de la superhidrofobicitat. Han estat investigats múltiples mètodes per intentar dipositar el laureat sobre la superfície activa dels substrats. El mètode amb resultats positius en promoure superhidrofobicitat ha estat l’electroquímic. Aquest mètode està basat en la immersió en una dissolució d’electròlit no aquosa de NiCl2 0.05 M conjuntament amb àcid lauric 30 g/L en etanol amb aplicació de corrent continu per generar una reacció electroquímica entre els reactius i el substrat. La reacció de reducció del níquel ha permès la formació de nuclis de níquel metàl·lic a la superfície de metall que han afavorit el dipòsit de compostos de laureat de níquel. L’acer inoxidable 316L tractat presenta una elevada superhidrofobicitat amb angles de contacte superiors a 160° en un rang de temps de reacció entre els 30 segons i els 15 minuts, a més, l’angle de lliscament que presenten aquestes superfícies és menor a 10° i totes tenen l’efecte d’autoneteja. Els millors resultats s’obtenen amb només 30 i 60 segons, amb angles de contacte de 175° i 172°, respectivament, on es troben presents pilars i illes, per tant, és un procediment fàcilment industrialitzable pels temps tan curts de producció. En el cas de l’acer inoxidable 304, s’han obtingut mostres superhidrofòbiques amb temps de reacció compresos entre els 30 segons i els 10 minuts, obtenint el màxim valor de 160° amb només 30 segons d’electròlisi on la superfície presenta pilars i petites illes, repetint-se les bones condicions per poder realitzar una producció a nivell industrial. El coure pur (UNS C10100) tractat per electròlisi amb la mateixa metodologia que els acers inoxidables, presenta superhidrofobicitat en un interval de temps comprés entre els 60 segons i els 15 minuts, obtenint-se el millor resultat amb 90 segons de temps d’electròlisi i angle de contacte de 160° on la primera capa s’ha format i comencen a formar-se de forma molt esporàdica alguns pilars. L’observació de mostres amb diferents temps de reacció, ha permès identificar els modes de creixement del revestiment generat. Els tres substrats on s’ha generat la superhidrofobicitat mitjançant l’aplicació del mètode electroquímic, no comparteixen el mateix mode de creixement. Els acers inoxidables segueixen el mode de Volmer-Weber, on el component original és el pilar i el creixement d’aquests pilars en vertical i horitzontal formen illes, finalment les illes es saturen fins cobrir completament l’àrea del substrat, per continuar creixent en vertical. Sorprenentment, en el coure pur 99,9% produït en condicions idèntiques als acers inoxidables, s’ha identificat el model de creixement del revestiment generat en un model 2D epitaxial o de Stransky-Krastanov, on el component inicial és una capa i posteriorment, el creixement de pilars en vertical i horitzontal que amb temps de reacció suficient, formen illes. L’anàlisi acurat dels resultats obtinguts per espectroscòpia de masses d’ions secundaris i de fotoelectrons han permès identificar els diferents compostos que s’han generat en les diferents reaccions sobre cada substrat, d’aquesta manera, s’ha proposat el mecanisme de reaccions que permet disposar del control del procés global per tots quatre substrats.
Surface modification allows to obtain different properties as to their intrinsic substrate ones and to preserve it from the environment. In the last decades, materials science is investigating for improving the material characteristics and there are numerous techniques applied to reach this goal. Obtaining four superhydrophobic metallic materials by surface modification has been the main goal of this doctorate thesis. The selected metal surfaces have been pure copper and aluminium, UNS C10100 and AA1070, respectively. Electrical devices are the main application of these two metals, because they are the best electrical conductors. A reduction of the contact between water and the metallic surface allows to improve their performance and durability. The selected alloys have been AISI 316L and AISI 304 steels because they are the most applied stainless steels. They exhibit good mechanical properties and corrosion resistance and they are usually employed in pharmaceutical and food industry. The proliferation of bacteria is higher in aqueous medium and elevated temperature; this is why superhydrophobic stainless steel can help to reduce the bacteria and seaweed development. Superhydrophobicity is a surface feature present into some animals and plants, their surfaces are characterized to produce a minimal interaction with the water, because when they connect, a contact angle higher than 150 degrees is produced. This effect is a consequence of both, the particular surface roughness and the low surface energy showed in their skin. The most iconic example of it is the Lotus leaf. Various civilizations have considered the Lotus plant as a symbol of purity because it presents extraordinary low wettability and self-cleaning effect. This effect is associated with the water insulation since in contact with dust particles, rainwater drops may roll by the surface and the dust settled on the leaf surface is wrapped by the rolling drop. Self-cleaning property applied to metallic surfaces can assist in both, environmental with complicated cleaning operations and with the strong requirements of sanitary conditions. Superhydrophobicity is associated to other attributes, they have anti- sticking effect as well as liquid components separation by their differing polarity with many innovative applications as can be the need of isolating organic contaminants in liquid phase, especially when it is a complex and expensive operation. Obtaining superhydrophobic artificial surfaces is called mimicking of Nature, and there are multiple studies that strive in recent years to obtain materials with these benefits and that the durability of this property will be guaranteed, both strategies have been also studied in this doctorate thesis. There are two main requirements for a superhydrophobic surface. They are mandatory simultaneously on the substrate: the low surface tension and the hierarchical surface roughness in which coexist microscale and nanoscale morphology. These features promote a reduction of contact between water and surface which contributes to the surface isolation. It is necessary to adjust the surface by modifying its composition with compounds able to lower its surface energy as fatty acids and fluoro-compounds can do because metal surfaces have a high surface energy. In this research, we have opted to work with species that are as much environmentally friendly as possible. For this reason, the use of fluorosilanes and derivatives has been discarded. This study has been focussed to optimize the manufacturing time and to simplify the technology used in order to guarantee a higher competitiveness. These premises would promote a scalable industrial production for our superhydrophobic materials. Superhydrophobic surfaces morphology and roughness have been largely studied as can be found in literature. But the main goal of this research is in addition the identification of the coating growth mechanisms as well as the reactions involved in them. These purposes allow distinguishing the process variables, the evolution of the structure by the reaction time and, finally, the influence into the global process of each one. All of these objectives are very important because the final product applications are determined by the characteristics of the generated layer. In the case of aluminium (UNS AA1070), the process consisted of an immersion into ethanol solution of hydrochloric acid (30%) and lauric acid (30 g/L), causing removing natural alumina and the formation of terraced features leading to microscale roughness generated on the surface. The formation of microscale terraced and pits promotes a composite solid- liquid-air interface that may form air pockets trapped in the valleys avoiding the surface- water contact. Stransky-Krastanov growth model has been identified in aluminium. Different reactions have been produced between reactants and aluminium surface that promotes the coating formed of aluminium laureate compounds and alumina. The measured water contact angle was larger than 150°. Alternative method has been investigated in order to improve corrosion resistance of the aluminium substrate, this new process is similar to the previous one, but it implicates an anodized step before of the lauric acid immersion. Good results in corrosion potential and superhydrophobicity are obtained with this method. The growth mechanism is strongly influenced by the anodized layer and a porous hexagonal morphology similar to the bee hives is generated after 60 minutes of anodizing. The reaction products between alumina, aluminium substrate and lauric acid have kept the previously anodized structure. Superhydrophobic stability of the coated aluminium in extreme low temperature (liquid nitrogen) has also been studied and the results let us conclude that the anodized and lauric acid immersed aluminium substrate can avoid the ice adhesion. Once returned to room temperature and humidity superhydrophobicity is kept. The stainless steels and copper have not responded positively to the same process applied to the aluminium substrate. Consequently, alternative methods have been applied in order to obtain superhydrophobicity. Various methods have been investigated to form laureate products on the active surface. Positive results promoting superhidrophobicity have been obtained by electrochemical process. The details of the process are as follows: metallic samples were immersed into an uniform electrolyte solution of nickel chloride (0.05 M) and lauric acid (0.1 M) in ethanol and a direct current voltage of 30 V was applied across the two electrodes in order to obtain an electrochemical reaction between the reagents and the surface. Nickel ions around the cathode have been reduced to metallic nickel on the cathodic surface, when the voltage is applied across the two electrodes. The metallic nickel will then act as growth site. Meanwhile, more nickel ions will react with the lauric acid and will form nickel laureate on the activated surface using metallic nickel as anchorage agent or growth site. Superhydrophobic surfaces on 316L stainless steel were developed via a short procedure (between 30 seconds to 15 minutes) with water contact angle greater than 160°. In addition, water rolling angles less than 10° have been obtained, as a result, these samples have presented self-cleaning effect. 30 and 60 seconds of reaction were enough to obtain optimum superhydrophobic 316 stainless steel surfaces with water contact angles of 175° i 172°, respectively. The morphology is formed by pillars and islands. These experimental conditions are easily scalable to industrial level. Superhydrophobic 304 stainless steel surfaces have been produced between 30 seconds to 10 minutes of electrolytic process. Sample with only 30 seconds of reaction time exhibited the best water contact angle of 160°, pillars and little islands have coated the active surface. As above, processing can be reproduced easily at industrial level. The same methodology of stainless steel samples has been applied to pure copper (UNS C10100) and superhydrophobicity has been obtained between 60 seconds and 15 minutes. Electrolysis time of 90 seconds was enough to reach the best result with a water contact angle of 160°. This sample presented a morphology characterized by an initial layer with some spread pillars. Reducing the reaction time allowed us to identify the growth mechanism of the produced coating. Superhydrophobic stainless steels and copper surfaces showed different growth mechanisms although the same coating process has been applied to all of them. Volmer- Weber growth mechanism has been identified in stainless steel, from the mechanism point of view, the building block is the pillar, followed by parallel and perpendicular growth of them, then islands of pillars saturate covering completely the surface and finally, the islands continue to grow perpendicularly to the substrate surface. Surprisingly, the growth mechanism of the superhydrophobic copper substrates has been identified as 2D-epitaxial model or Stransky-Krastanov model. We must remember that copper surfaces were obtained with the same process as stainless steel substrates. Stransky-Krastanov model started forming one layer over the substrate surface then the pillars were formed and grow parallel and perpendicular. Finally, if the reaction time is sufficient, islands of pillars will also growth. High resolution mass spectroscopy of secondary ions (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) analyses allowed us to identify the species responsible for the superhydrophobicity in all the methods applied, thanks to these results, the involved chemical reactions mechanisms have been proposed which allow us to control the global process for all four metallic substrates.

La presente tesis doctoral titulada ¿Materiales funcionales híbridos para el reconocimiento óptico de explosivos nitroaromáticos mediante interacciones supramoleculares¿ se basa en la combinación de principios de Química Supramolecular y de Ciencia de los Materiales para el diseño y desarrollo de nuevos materiales híbridos orgánico-inorgánicos funcionales capaces de detectar explosivos nitroaromáticos en disolución. En primer lugar se realizó una búsqueda bibliográfica exhaustiva de todos los sensores ópticos (cromogénicos y fluorogénicos) descritos en la bibliografía y que abarca el periodo desde 1947 hasta 2011. Los resultados de la búsqueda están reflejados en el capítulo 2 de esta tesis. El primer material híbrido preparado está basado en la aplicación de la aproximación de los canales iónicos y, para ello, emplea nanopartículas de sílice funcionalizadas con unidades reactivas y unidades coordinantes (ver capítulo 3). Este soporte inorgánico se funcionaliza con tioles (unidad reactiva) y una poliamina lineal (unidad coordinante) y se estudia el transporte de una escuaridina (colorante) a la superficie de la nanopartícula en presencia de diferentes explosivos. En ausencia de explosivos, la escuaridina (color azul y fluorescencia intensa) es capaz de reaccionar con los tioles anclados en la superficie decolorando la disolución. En presencia de explosivos nitroaromáticos se produce una inhibición de la reacción escuaridinatiol y la suspensión permanece azul. Esta inhibición es debida a la formación de complejos de transferencia de carga entre las poliaminas y los explosivos nitroaromáticos. En la segunda parte de esta tesis doctoral se han preparado materiales híbridos con cavidades biomiméticas basados en el empleo de MCM-41 como soporte inorgánico mesoporoso (ver capítulo 4). Para ello se ha procedido al anclaje de tres fluoróforos (pireno, dansilo y fluoresceína) en el interior de los poros del soporte inorgánico y, posteriormente, se ha hidrofobado el interior de material mediante la reacción de los silanoles superficiales con 1,1,1,3,3,3-hexametildisilazano. Mediante este procedimiento se consiguen cavidades hidrófobas que tienen en su interior los fluoróforos. Estos materiales son fluorescentes cuando se suspenden en acetonitrilo mientras que cuando se añaden explosivos nitroaromáticos a estas suspensiones se observa una desactivación de la emisión muy marcada. Esta desactivación de la emisión es debida a la inclusión de los explosivos nitroaromáticos en la cavidad biomimética y a la interacción de estas moléculas (mediante interacciones de ¿- stacking) con el fluoróforo. Una característica importante de estos materiales híbridos sensores es que pueden ser reutilizados después de la extracción del explosivo de las cavidades hidrofóbicas. En la última parte de esta tesis doctoral se han desarrollado materiales híbridos orgánicoinorgánicos funcionalizados con ¿puertas moleculares¿ que han sido empleados también para detectar explosivos nitroaromáticos (ver capítulo 5). Para la preparación de estos materiales también se ha empleado MCM-41 como soporte inorgánico. En primer lugar, los poros del soporte inorgánico se cargan con un colorante/fluoróforo seleccionado. En una segunda etapa, la superficie externa del material cargado se ha funcionalizado con ciertas moléculas con carácter electrón dador (pireno y ciertos derivados del tetratiafulvaleno). Estas moléculas ricas en electrones forman una monocapa muy densa (debida a las interacciones dipolo-dipolo entre estas especies) alrededor de los poros que inhibe la liberación del colorante. En presencia de explosivos nitroaromáticos se produce la ruptura de la monocapa, debido a interacciones de ¿-stacking con las moléculas ricas en electrones, con la consecuencia de una liberación del colorante atrapado en el interior de los poros observándose una respuesta cromo-fluorogénica
Salinas Soler, Y. (2013). Functional hybrid materials for the optical recognition of nitroaromatic explosives involving supramolecular interactions [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31663
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Superhydrophobic coatings (SHC) with excellent self-cleaning and corrosion resistance property is developed on magnetite coated AISI SAE 1020 steel by using a simple immersion method. Roughness measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), contact angle measurement (CAM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and qualitative characterization of self-cleaning behavior, antifouling property and durability of the coatings are assessed. A water contact angle as high as 152o on the coated surface with excellent self-cleaning and resistivity to corrosion and good longevity in atmospheric air is obtained. Self-cleaning test results prove that these surfaces can find applications in large scale production of engineering materials. Potentiodynamic polarization tests and EIS tests confirm that the superhydrophobic low carbon steel surfaces have better resistance to corrosion compared to bare steel and magnetite coated steel in 3.5% NaCl solution. But the longevity of the coated steel surfaces in 3.5% salt solution is limited, which is revealed by the immersion durability test. However, hydrophobic coatings (HC) have better stability in normal tap water, and it can stay unharmed up to 15 days. Finally, hydrophobic coatings on low carbon steel surface retains hydrophobic in open atmosphere for more than two months. Results of this investigation show surface roughness is a critical factor in manufacturing hydrophobic steel surfaces. Higher contact angles are obtained for rougher and more uniform surfaces. A linear mathematical relationship (y =6x+104; R2 = 0.93) is obtained between contact angle (y) and surface roughness (x).

Textile processing methods such as conventional exhaustion dyeing, pre-treatments and printing consume high amounts of water and use partly toxic and hazardous chemicals which are non-degradable. These chemicals (e.g. excess amount of dye, additives and catalysts) remain partially in the waste-water which is drained out and ends up polluting the environment. The supercritical carbon dioxide dyeing technology presents an eco-friendly and water-free method with reduced use of chemicals and energy. The benefits of such technology are currently not overcoming the relative high investment costs which impede its full implementation into the textile industry. This study presents an approach to extent the application of the eco-friendly supercritical carbon dioxide technology. It combines the well-studied supercritical carbon dioxide dyeing process for polyester with the functionalisation process to obtain water repellent surface properties. As water repellent (substance) environmentally benign silicones are used. Results showed that the simultaneous dyeing and functionalisation process was feasible assessed by the compatibility of the dye and silicone in the system. Silicone and dye did not interfere in each other’s functionality (colour strength and water contact angle). Further the process temperature and silicone molecular weight showed no influence on the colour strength of the fabric whereas the water contact angle (water repellence) increased with increasing temperature. The resulting polyester fabric showed acceptable colour strength yet did not obtain sufficient water repellent properties despite the increase in water contact angle of the treated samples to the untreated reference sample. The poor water repellence is suggested to be caused by the hydrophobic functional groups of the silicones oriented towards each other rather than toward the outer fabric surface. Overall the thesis is promoting research which combines eco-friendly technologies including environmental benign chemicals for the textile industry. Silicones are widely used in textile processing not only as water repellents, but also as anti-foaming agents, lubricants and softeners. Therefore a water-free and eco-friendly application method can benefit a wide range of finishing processes.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xix, 343 p.; also includes graphics (some col.) Includes bibliographical references (p. 325-343).

The biggest challenge with magnesium alloy biodegradable implants is the rapid corrosion at the earlier stages of the healing process after implantation. In this research, the impact of surface roughness generated by different means on the corrosion rate of AZ31 magnesium alloy in a simulated biologic environment is investigated. In order to perform accurate experimentation, an in vitro setup is assembled that simulates the human body environment accurately has been prepared using Schinhammer’s in vitro immersion testing setup and Kokubo’s Simulated Body Fluid (SBF). For the immersion test of Mg in SBF, several surface texture groups of Mg have been prepared and submerged into the in vitro tank. The Mg samples’ comparative analysis has been made in terms of corrosion rate, total weight loss and hydrogen gas evolution within a span of 7 days for the first experiment to narrow down the scope and 14 days for the follow up experiment. After 14 days of in vitro immersion test with varying roughness and hydrophobic modifications such as Cytop coating and stearic acid modification, it has been observed that the roughness group created by etching in aqueous NaCl solution for three minutes, shows better corrosion resistance compared to the polished control group. Hydrophobic modifications on the surfaces did not affect the corrosion behavior significantly.

For the last 10 years, silicone-based admixtures have been successfully used for bulk waterproofing treatment of cementitious materials. However, a reduction in mechanical properties of treated materials is rather observed and becomes a major problem for the in-situ application. A new concept of a knowledge-based integral water repellent has been designed in such a way that the negative effect on mechanical properties is significantly reduced. The technology comprises the delayed release of the hydrophobic agent (silicone resin) which is achieved by encapsulation of the resin in SiO2 shell. A multidisciplinary research was conducted in order to propose a model of the delayed release and the silica shell reaction mechanism in cement paste. Therefore, a study on the microcapsules reaction in calcium hydroxide solution was conducted by means of FTIR, DSC-TGA, surface tension measurements and chemical analysis by ICP-OES. It was shown that microcapsules flocculate in presence of Ca2+, what appears to be the main factor that contribute to the delayed release of the resin.The influence of the microcapsules on Ordinary Portland (OPC) and Blast furnace slag (BFS) cement hydration process was compared with the emulsion of silane monomer and silicone resin. It was shown that the emulsion delays the setting and influences the early age hydration by prolonging the dormant period and decreasing the hydration heat. Cement microstructure and hydration products development was observed by SEM/ESEM. Quantitative analysis of hydration products was assessed by Rietveld analysis of XRD diffractograms. Emulsion induced a significant delay in the cement paste setting by changing the amount and morphology of ettringite and portlandite at very early age. Differently, microcapsules didn’t show any effect on these properties. Experimental work on relevant mortars is done in order to prove the concept of a delayed release as a solution towards the decrease in mechanical properties. The influence of the new additive on setting, volume change, dynamic E-modulus and the compressive strength was analysed. New analytical techniques (AutoShrink, Ultrasonic Pulse Velocity and ConSensor) in combination with traditional ones (Penetration resistance test and compressive strength on cubes) were used. Microcapsules have successfully lowered the negative impact of silanes on the compressive strength and dynamic Young’s modulus. Moreover, it was showed that the microcapsules slightly influence autogenous deformation by increasing the shrinkage of mortars.Microencapsulation of the silicone resin proved to be a promising solution for the bulk hydrophobic treatment of cementitious materials with no-influence on cement hydration.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

L'objectif de ces travaux de thèse concerne l'étude de l'apport de la chimie supramoléculaire à différents niveaux de la science membranaire. Lors de la première partie de nos travaux, nous avons étudié les capacités d'auto-organisation dynamique de molécules bolaformes. Des études de caractérisations ont permis de déterminer différentes structures, dont la formation de canaux ioniques ou aqueux pour certaines. Les capacités de transport de ces molécules auto-assemblés au sein de bicouches lipidiques a été déterminé. Une autre étude concerne l'utilisation d'un milieu hydrophobe, par des interactions supramoléculaire de type forces de Van der Waals, pour confiner de nouvelles fonctionnalisations dans des matériaux mésoporeux. Différents matériaux, dont les utilisations varient avec les molécules confinées, ont été obtenus et caractérisés par plusieurs méthodes d'analyses. Suite à ces résultats, nous avons spécifiquement étudié et optimisé l'utilisation de matériaux silicés électrodéposés sur la surface d'électrodes, puis fonctionnalisés par des chaînes alkyles, pour former des capteurs électrochimiques en étudiant le cas du fullerène
The main objective of this study concerns the contribution of supramolecular chemistry at different level of membrane science. During the first part of our work, we have studied the dynamic self-organizing capacities of bolaform molecules. Different characterization techniques allowed us to define different structures, including ion or water channels for some of them. Transport capacities of those self-assembling molecules through lipid bilayers have been determined by several tests. Another study is about the use of a hydrophobic environment, by supramolecular interactions such as Van der Waals forces, to confine new functionalization inside mesoporous materials. Different materials, which use is determined by the confined molecules, have been obtained and characterized by several analysis methods. Furthermore, we have studied and optimized the use of electrodeposited silice materials on electrodes surface, then functionalized by alkyl groups, to form electrochemical captors by studying specifically the fullerene case

Dans ce cadre de cette thèse, nous nous intéressons à la conception, à la synthèse et à la caractérisation des propriétés physicochimiques de dérivés lipophiles d’extractibles du bois. Nous avons ainsi envisagé de modifier la structure de trois flavonoïdes dont la ressource est importante à partir de différentes essences de bois : la catéchine, le mesquitol et la naringénine pour incorporer des fonctionnalités supplémentaires. Les applications visées ici concernent principalement la protection des matériaux, en l’occurrence le bois et les métaux corrodables. En ce qui concerne la préservation du bois, il semble possible d’envisager différentes stratégies pour inhiber l’action de dégradation des champignons sur le bois. L’imprégnation des composés antioxydant tels que les polyphénols dans le bois, seuls ou en association avec un biocide pour agir en synergie, permet de limiter les effets des radicaux ou autres oxydants utilisés et générés par les pourritures, L’objectif de la modification structurale est ici d’augmenter leur hydrophobie pour limiter leur lessivage en cas d’utilisation du matériau en conditions extérieures. La deuxième application visée est la protection des matériaux métalliques. En effet, l’utilisation des produits antioxydants naturels comme inhibiteur de corrosion permet de substituer les inhibiteurs inorganiques ou les molécules organiques d’origine pétrochimique (polyamines, Imidazole…), car leur production est coûteuse et elles sont issues de ressources non renouvelables. Le greffage d’une chaîne hydrocarbonée hydrophobe sur des polyphénols ayant des propriétés antioxydantes permet d’obtenir un film protecteur sur le matériau
Within the framework of this thesis, we are interested in the design, synthesis and characterization of the physicochemical properties of lipophilic derivatives of wood extractives. We have thus considered modifying the structure of three flavonoids whose resource is important from different wood species: catechin, mesquitol and naringenin to incorporate additional functionalities. The applications reported here mainly deal with the protection of materials like wood and corrodible metals. With respect to wood preservation, it seems possible to consider different strategies to inhibit the wood degradation related to fungi on wood. Impregnation of antioxidant compounds such as lipophilic polyphenols on wood can limit the effects of radicals or other oxidants used and generated by rots. The second intended application is the protection of metallic materials. Indeed, the use of natural antioxidants as a corrosion inhibitor replace inorganic inhibitors or organic molecules (polyamines, imidazole...), because their production is expensive and toxic. The grafting of a hydrophobic hydrocarbon chain on polyphenols which have antioxidant properties allows the formation of protective films on the material

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2005.
Bidstrup Allen, Sue Ann, Committee Member ; Ludovice, Peter, Committee Member ; Hess, Dennis, Committee Chair ; Henderson, Clifford, Committee Member ; Patterson, Timothy, Committee Member.

A la natura existeixen diferents animals o plantes com ara els sabaters (Gerris remigis), la flor de lotus (Nelumbo nucifera) o les fulles d’arròs (Oriza sativa) que presenten propietats extraordinàries com ara l’auto-neteja o bé la resistència enfront l’erosió ambiental. Aquestes propietats estan directament relacionades amb l’estructura així com també la composició química. En els darrers anys, la ciència de materials ha reproduït aquestes superfícies naturals per a millorar aquestes peculiars propietats. Aquest fet ha establert un nou escenari per a les superfícies superhidrofòbiques anomenat biomimetisme. Aquestes superfícies estan constituïdes per dos nivells diferents. El primer és la microestructura mentre que el segon és la nanoestructura final del sistema. La combinació d’aquestes dues característiques porta a generar una estructura jeràrquica que és un factor determinant en les superfícies superhidrofòbiques. De fet, aquestes característiques augmenten la rugositat superficial que combinat amb alguns compostos químics, com ara l’àcid làuric, tendeixen a disminuir la tensió superficial. D’aquesta manera, l’angle de contacte entre la superfície i una gota d’aigua augmenta fins a assolir valors majors a 150°. A més, aquesta innovadora propietat conferida a les superfícies, coneguda també com a supermullabilitat, obre un nou escenari ja que el comportament de mullabilitat canvia d’un estat superhidrofòbic a un de superoleofílic quan el sistema sòlid-aigua-aire es canviat per un de sòlid-aigua-oli. Cal destacar que la sostenibilitat dels materials i en particular la de les superfícies superhidrofòbiques ha esdevingut una àrea d’especial d’interès en els darrers anys donada una marcada determinació per preparar materials nous i sostenibles. Els compostos fluorats han estat uns dels reactius més comuns per generar superfícies amb propietats d’hidrofobicitat. Cal tenir en compte però que són compostos extremadament perjudicials per al medi ambient així com també per a les persones. En aquest sentit doncs, cal considerar l’ús de materials i reactius més sostenibles per aplicacions exteriors, on sovint s’empren diferents processos químics i físics per minimitzar aquest efecte perjudicial. L’objectiu d’aquesta tesi doctoral és la síntesi, caracterització i estudi de la degradació de la superhidrofobicitat emprant, en l’extensa varietat de compostos naturals i àcids grassos disponibles, l’àcid làuric com a principal reactiu per disminuir la tensió superficial en els sistemes metàl·lics. Les tècniques de caracterització són d’especial interès per a determinar la relació entre la composició, l’estructura i les propietats superficials. A la vegada, aquestes permeten determinar els mecanismes involucrats en la formació del recobriment. Per aquest motiu, tècniques com l’Espectroscòpia Fotoelectrònica (XPS) o l’Espectroscòpia Infraroja per transformada de Fourier (FTIR) permeten identificar la composició química del recobriment superhidrofòbic a nivell de superfície. Així mateix, les tècniques mmicroscòpiques com l’Electrònica de Rastreig amb Emissió de Camp són particularment interessants per estudiar la morfologia de la superfície. Aquesta tesi es centra en tres sistemes superhidrofòbics diferents que s’han obtingut emprant rutes alternatives. D’una banda, el mètode per generar el recobriment ha estat l’electrodeposició. I d’altra banda, la molta d’elevada energia combinada amb el dipòsit en fase líquida. Aquests sistemes superhidrofòbics són altament resistents en front agents ambientals com ara l’abrasió o l’exposició a la llum UV. Considerant les propietats superficials dels sistemes superhidrofòbics obtinguts, s’han proposat diferents aplicacions com a estratègies innovadores per al seu ús a l’exterior com ara la separació d’oli en aigua, la recollida d’aigua de boira i l’eliminació de coure (II) de solucions aquoses. En resum, aquesta tesi doctoral posa de manifest tres sistemes superhidrofòbics innovadors que s’apliquen per poder solucionar problemes ambientals globals com és la separació d’oli en aigua o bé la recollida d’aigua de boira. Aquestes propostes obren una finestra d’oportunitat en la purificació d’aigües en el cas dels abocaments o bé la recollida d’aigua en zones que pateixen sequera severa.
In nature there are several animals or plants such as pond skaters (Gerris remigis), Lotus flower (Nelumbo nucifera) or rice leaves (Oriza sativa) that possess extraordinary capabilities like self-cleaning properties or resistance against environmental erosion. These properties are directly related to their structure as well as to their chemical composition. For the last years, materials scientists have tried to reproduce these natural surfaces to enhance these particular properties over materials surfaces. These modified surfaces are build up in two different levels. The first one is the microstructure and the second one corresponds to the nano contribution to the final system. The combination of both features leads to a hierarchical structure that is a key parameter for superhydrophobic surfaces. Indeed, these characteristics increase the surface roughness that combined with some chemical compounds such as fatty acids, make the surface energy decrease. In contrast, the contact angle between the surface and the water droplet increases until it reaches values higher than 150°. In addition, this innovative property conferred to the surfaces, also known as superwettabability, opens a new scope as the wetting behaviour switches from a superhydrophobic state to a superoleophilic one when the solid-water-air system is changed to a solid-water-oil one. This thesis is focused on three different superhydrophobic systems that have been obtained following alternative routes. On one hand the method for the coating formation is carried out by electrodeposition. On the other hand, high-energy ball milling is combined with liquid phase deposition. Additionally, the superhydrophobic systems are highly resistant against environmental effects such as abrasion or under UV light exposure. Taking into account the surface properties of the as prepared superhydrophobic systems, different applications are proposed as innovative strategy for their use outdoors such as oil in water separation, water harvesting from fog and copper (II) removal from aqueous solutions. In summary, this PhD thesis puts forward three innovative superhydrophobic systems applied to solve worldwide environmental problems such as oil in water separation and water harvesting from fog. These solutions opens a new scope in water purification in case of oil spill disasters or water collecting in lands that are experiencing water scarcity.

Contaminated soils and sediments have been identified as significant secondary sources of organic contaminants.  Leaching tests may be useful tools to estimate the mobility of contaminants via the water phase and thereby the risk for groundwater and surface water contamination. The influence of soil composition (peat and clay content) on the leachability was investigated in batch leaching experiments for chemically diverse hydrophobic organic compounds (HOCs: PCP, PAHs, HCB, HCHs, PCBs, and TCDD/Fs). The above mentioned compounds were analyzed by both GC-LRMS (gas chromatography coupled with low resolution mass spectrometry (GC-HRMS) and GC-HRMS (gas chromatography coupled with high resolution mass spectrometry). Also the the leachability of eleven selected PCBs from naturally aged soil (Västervik, Sweden) was investigated in relation to the composition and concentration of dissolved organic matter at different pH (2 to 9), using a pH static test with initial acid/base addition. The the composition and of dissolved organic matter (DOM) at different pH values was explored by FTIR spectroscopy. The results were evaluated by orthogonal projections to latent structures (OPLS). Generally, for all model compounds studies, the Kd-values showed a variability of 2-3 orders of magnitude depending on the matrix composition. The Kd-values of moderately hydrophobic compounds, (e.g. HCHs, PCP and Phe), were correlated mainly with the organic matter content of soil. For more hydrophobic compounds (e.g.BaA, HCB and PCB 47), the leachability decreased as the proportions of  OM and clay contents increased. The Kd-values of 1,3,6,8-TCDD and 1,3,6,8-TCDF were  positively correlated with peat content but negatively correlated with clay content, while for PCB 153 and PCB 155 the correlations were reversed. The log Kd-values of all target PCBs decreased with increased pH values and the log Kd-values were highly correlated with the concentration of total organic carbon (TOC) in the leachates. The FTIR analysis of DOM showed that the least chlorinated and hydrophobic PCB congeners (i.e. PCB 28) might be associated with the hydrophilic fraction (i.e. carboxylic groups) of DOM. Our study demonstrated how complex interaction between the organic matter, clay components, pH and DOC influences the leachability of HOCs in a compound-specific manner.

Betulin is a naturally abundant compound in the outer bark of birch and can be easily obtained by solvent extraction. Herein, solutions of betulin were used to treat cellulosic textile fibers and improve their water repellency. Cotton fabrics impregnated in a 7.5 g L-1 solution of betulin in ethanol showed the highest water contact angle of about 153° while the impregnation in a 3.75 g L-1 solution resulted in a close effect. A terephthaloyl chloride-betulin copolymer was synthesized and dissolved in tetrahydrofuran to afford a solution with a concentration of 3.75 g L-1. The cotton fabric impregnated in this solution showed a water contact angle of 150°. Changes in morphology of the cellulose fibers before and after the treatment were observed by scanning electron microscopy, and the water repellency was measured by a standard spray test. The marketing strategy of the potential product, which will be developed based on this technique, was discussed.

Forcer l'intrusion d'un liquide dans une matrice nanoporeuse non-mouillante requiert de porter le liquide à des pressions élevées de l'ordre de quelques dizaines de mégapascals. Quand l'imbibition forcée du liquide dans le volume poreux à haute pression est réversible, l'ensemble poreux/liquide, alors qualifié de système hétérogène lyophobe (SHL), peut-être mis en oeuvre comme convertisseur d'énergie mécanique en énergie interfaciale avec des densités de puissance avantageuses par rapports aux solutions techniques actuelles (supercapacités, accumulateurs hydrauliques). La compréhension physique des SHL en régime dynamique est donc déterminante pour les applications potentielles. Afin d'étudier les processus de remplissage et vidange à l'oeuvre dans les SHL, un dispositif appelé intrusiomètre dynamique a été amélioré et qualifié afin de pouvoir sonder ces processus sur trois décades de temps, pour des températures allant de -5° à 70° et jusqu'à une pression de 100MPa. Deux matrices poreuses sont employées. Le premier matériau est un hydride organo-silicique à porosité ordonnée indépendante qui a été synthétisé puis rendu hydrophobe par fonctionnalisation. Les mesures dynamiques conduites sur ce solide rendent compte de la structuration microscopique de sa surface poreuse par le biais d'un modèle d'ancrage/relaxation de la ligne triple lors de l'intrusion du liquide, et de la pertinence de la nucléation d'une bulle de vapeur comme processus limitant l'extrusion. Le second matériau, le ZIF-8, qui présente des pores sub-nanométriques, a été employé pour explorer des phénomènes dissipatifs présents lors de mesures dynamiques.Par ailleurs, l'étude du transport de soluté vers le coeur du poreux est explorée. Un dispositif original a été conçu afin de pouvoir changer le liquide en conservant le poreux. Des mesures cycliques en solutions salines étendent ainsi la compréhension du rôle du soluté vis-à-vis du poreux. En particulier, la diffusion lente du soluté dans le volume poreux après intrusion est établie et une hypothèse de cristallisation des ions dans la nanoporosité est proposée afin d'interpréter les mesures obtenues
Tens of megapascals of hydrostatic pressure are requiered in order to force the intrusion of a liquid into a non-wetting nanoporous matrix. When the reversibility of this forced imbibition exists, the pair porous matrix/liquid is called a lyophobic heterogeneous system. Those systems may be used to convert mechanical energy into interfacial one with power densities attractive compared to other conversion devices. The fundamental description of LHS in the dynamical regime is thus of prime interest considering applications. A dynamical intrusiometer as been upgraded in order to study the filling and drying of the nanoporous matrices over three orders of magnitude in time and over the temperature range -5° to 70° up to 100MPa. Two porous matrices have been studied. The first one is a periodic mesoporous organosilica which has been synthetised and grafted so as to render it non-wetting. The microscopic order of the porous surface is related thanks to a pinning/depinning model for the contact line motion during the intrusion, while the nucleation of a vapor bubble is shown to be still relevant to describe the extrusion. A more thorough investigation for dissipative phenomena is conducted in the sub-nanometer porous matrix ZIF-8. Solute transport in this material is also presented. To this end, a new device has been designed to allow the renewal of the liquid while keeping the powder. Cyclic measures could then broaden the understanding of the influence of the solute on the matrix. The main conclusions being a slow diffusion of ions in the grains and a crystallisation of the solute when drying occurs

Une surface superhydrophobe est caractérisée par un angle de contact apparent supérieur à 150° et un angle de contact dynamique faible. Ce phénomène, découvert dans la nature, suscite une grande attention de la part de la communauté scientifique. En effet, le contrôle de la mouillabilité d’une surface solide est important dans de nombreuses applications. De nombreuses techniques d’élaboration de surfaces superhydrophobes ont été décrites, dont la polymérisation par voie électrochimique qui permet d’obtenir des surfaces avec une mouillabilité variée, de façon contrôlée et en utilisant des polymères conducteurs. Le développement de matériaux à mouillabilité réversible, sensibles aux stimuli extérieurs revêt un grand intérêt pour leurs diverses applications potentielles. Le but de ce travail de thèse est d’élaborer des matériaux superhydrophobes réversibles par l’utilisation de polymères conducteurs électrodéposés. Nous avons obtenu des surfaces superhydrophobes par introduction de monomères hydrophiles ammoniums. Des changements de la mouillabilité ont été obtenus en utilisant la réduction par voltage et l’échange d’ions. Des propriétés réversibles hydrophobes / hydrophiles ont aussi été atteintes par post-fonctionnalisation de surface par différents acides boroniques
Superhydrophobic surface is characterized by an apparent contact angle higher than 150° and a low dynamic contact angle. This phenomenon, found in nature, arouses great attention from the scientific community. Indeed, controlling the wettability of a solid surface is important in many applications. Many techniques to prepare superhydrophobic surfaces have been described, including the electrochemical polymerization which allows to obtain surfaces with various wettability by a controlled way and using conductive polymers. The development of materials with switchable wettability, sensitive to external stimuli is of great interest for their potential applications. The aim of this thesis is the development of reversible superhydrophobic materials by using conducting polymers. We obtained superhydrophobic surfaces by using hydrophilic ammonium monomers. Changes in wettability were obtained by dedoping and ion exchange. Reversible hydrophobic / hydrophilic properties were achieved by surface post-functionnalization using differents boronic acids

Dans ce travail, nous nous sommes intéressés à la synthèse de nouveaux hydrogels, obtenus en réticulant chimiquement, par une réaction thiol-ène, des polyélectrolytes (PAA) modifiés par des groupes alkyle greffés le long de la chaîne. L'hydrogel ainsi formé est donc composé d'un réseau à la fois physique, du à l'agrégation des groupements hydrophobes en micelles, et chimique. Par comparaison avec un hydrogel de PAA « modèle » (non hydrophobe), nous étudions les phénomènes dissipatifs que le réseau transitoire peut induire, en nous intéressant plus spécialement aux grandes déformations, par le biais d'expériences de compression uniaxiale. Dans le domaine d'élasticité linéaire, nous avons identifié une forte composante viscoélastique due aux agrégats hydrophobes, ceux-ci n'affectant cependant pas le module élastique du gel, comparativement au gel non modifié. Les expériences aux grandes déformations ont mis en évidence un mécanisme supplémentaire d'agrégation causé par des interactions électrostatiques attractives entre chaînes de PAA. Ce phénomène, induit par la déformation, est fortement couplé à la dissipation d'énergie causée par les réorganisations des agrégats hydrophobes soumis à la contrainte. Les agrégats hydrophobes améliorent de façon non négligeable la résistance à la rupture du réseau comparativement aux gels non modifiés. Des résultats préliminaires de fracture sont également présentés.

Nous décrivons un procédé de coacervation original et polyvalent qui permet d'encapsuler des substances hydrophobes dans l'eau avec un contrôle précis des propriétés de la dispersion finale. Le composé hydrophobe est d'abord émulsionné dans une solution aqueuse d'un polyélectrolyte amphiphile à squelette hydrophobe de type " alkali-swellable ". Un changement des conditions physicochimiques (pH, force ionique) provoque alors la précipitation du polymère à la surface des gouttelettes hydrophobes. Notre travail s'organise suivant trois directions complémentaires. Tout d'abord, nous nous attachons à comprendre la microstructure des solutions de polymères, d'où découlent en partie leurs propriétés interfaciales. Pour cela, nous développons une méthode originale de détection d'agrégats hydrophobes qui exploite le solvatochromisme du Rouge du Nil. Puis, nous analysons les propriétés rhéologiques linéaires et non linéaires des solutions de copolymères -viscosité, forces normales, fracturation aux grandes déformations- en relation avec la composition des chaînes et les caractéristiques physicochimiques des solutions. Enfin nous posons les bases d'un modèle d'émulsification dans des phases continues viscoélastiques. Ce cadre conceptuel permet de relier l'architecture et la composition des copolymères amphiphiles utilisés à leurs propriétés rhéologiques en solution et aux caractéristiques de la dispersion obtenue à la fin du procédé. Il est ainsi possible de définir à priori les conditions optimales qui permettront d'encapsuler à façon une large gamme de substances hydrophobes.

Par coacervation complexe, en choisissant le tensioactif approprié et en jouant sur le ratio molaire tensioactif/polymère, il est possible de faire précipiter un polymère à la surface de gouttelettes d'huile : le complexe insoluble polymère/tensioactif obtenu forme alors la membrane des micro-capsules dont le cœur hydrophobe peut contenir des molécules apolaires. Cette thèse est une étude de trois systèmes polymère/tensioactif de charge opposée pouvant constituer la paroi insoluble des micro-capsules. Le tensioactif anionique utilisé est le Sodium Dodecyl Sulfate (SDS) et les polymères choisis sont un chitosane, un chitosane modifié hydrophobe et une gélatine de type A. Les interactions physiques et hydrophobes (en absence de sel) entre ces différents polymères et le tensioactif sont caractérisées par micro-calorimétrie de titration, tensiométrie, conductimétrie, viscosimétrie, mesures de mobilités électrophorétiques et détermination des isothermes de complexation du SDS aux polymères.

El polidimetilsiloxano (PDMS) es un polímero amorfo en base inorgánica con grupos pendientes que le imparten hidrofobicidad que es ampliamente utilidado en aplicaciones biomédicas. Debido a la baja energía superficial del PDMS, su adhesión es pobre. En algunas aplicaciones biomédicas (catéteres, prótesis) se requiere adhesión para lo cual se modifica superficialmente. Los plasmas generados en condiciones de no-equilibrio, también llamados plasmas fríos, han sido utilizados en el tratamiento superficial de PDMS para aumentar su energía superficial, pero las modificaciones producidas son poco estables, produciéndose una rápida recuperación de la hidrofobicidad (hydrophobic recovery). La estabilidad de las modificaciones superficiales del PDMS depende de las características del plasma utilizado para su tratamiento, por lo que el objetivo de la tesis doctoral se centra en la utilización de diferentes tipos de plasmas fríos para modificar las propiedades superficiales de PDMS de manera que simultáneamente se aumente su estabilidad y se mejore su adhesión. Otro aspecto innovador en el estudio consiste en la discriminación y optimización de las condiciones de tratamiento con plasma utilizando un diseño estadístico de experimentos, lo que he permitido modelar el efecto del tratamiento con plasma de superficies de PDMS empleando los ángulos de contacto y la química superficial como variables respuesta. Se ha estudiado el efecto de los diferentes tipos de plasma en la hidrofobicidad y la energía superficial del PDMS mediante medidas de ángulo de contacto. Las modificaciones en la química superficial han sido evaluadas usando espectroscopia infrarroja en modo de reflectancia total atenuada (FTIR-ATR) y espectroscopia fotoelectrónica de rayos X (XPS), mientras que los cambios en la morfología y nanorugosidad superficial se monitorizaron usando microscopía electrónica de barrido (SEM) y microscopía de fuerza atómica (AFM). Las propiedades de adhesión del PDMS se evaluaron mediante ensayos de adhesión en pelado en T y de cizalla a solape simple, utilizando un adhesivo sensible a la presión (PSA) en base acrílica para uso médico. Estas propiedades fueron además monitorizadas en función del tiempo tras el tratamiento con plasma para determinar la estabilidad de las modificaciones producidas. En general, el tratamiento superficial de PDMS con plasma produce oxidación de las cadenas de polisiloxano por sustitución de los grupos metilo por grupos hidroxilo, lo que aumenta la polaridad y la energía superficial, incrementando las propiedades de adhesión. Se produce el entrecruzamiento de cadenas mediante condensación de los grupos hidroxilo, formando una delgada capa superficial con estructura de sílice. Cuando las características del plasma son demasiado agresivas aparecen grietas superficiales favoreciendo la recuperación hidrofóbica por difusión de especies apolares desde el seno del PDMS hacia la superficie, así como por la reorientación de los nuevos grupos polares en la superficie hacia el seno del material. Este fenómeno se minimiza optimizando las condiciones de tratamiento empelando un diseño estadístico de experimentos. En sistemas de generación de plasma a baja presión, tratamientos con baja potencia durante largos tiempos mejoran la funcionalización de la superficie del PDMS, y el uso de mezclas de argón y oxígeno como gas plasmógeno resulta más efectivo que el empleo de los gases puros; la presión de trabajo tiene un papel fundamental en la estabilidad de las modificaciones producidas. En sistemas de antorcha de plasma atmosférico el tiempo de tratamiento y la distancia de la boquilla a la superficie son los parámetros más relevantes en la oxidación superficial del PDMS, mientras que en sistemas de plasma atmosférico de doble barrera dieléctrica, el voltaje, el tiempo de tratamiento y la distancia entre electrodos son las variables críticas en la efectividad del tratamiento superficial. Finalmente, la deposición de monómeros mediante antorcha de plasma permite generar nanoestructuras superficiales en el PDMS aportándole características de superhidrofobicidad.

Hydrophobic dipeptide crystals recently emerged as novel “organic zeolites” featuring tailorable pore size. In fact, seven out of nine pairwise combinations of L-isoleucine, L-valine and L-alanine amino acids crystallize according to the same charge-assisted hydrogen bond pattern, generating a family of microporous materials with right-handed 1D channels, having diameters in the sub-nanometer domain (<6Å), aliphatic environment and different degrees of helicity. The relationship between pore size and material properties was investigated with respect to gas separation, exploiting the affinity of carbon dioxide for the hydrophobic nanochannels of L-alanyl-L-valine (AV), L-isoleucyl-L-valine (IV) and L-valyl-L-isoleucine (VI). Reversible CO2 capture from an equimolar mixture of CO2 and methane, at room temperature and 1 atmosphere, was demonstrated with increasing purification performance with decrease in pore size. Dipeptide were also used as nanovessels in radical polymerizations with the aim of controlling otherwise non-specific reactions. Diene monomers (trans-1,3-pentadiene and isoprene) only yield linear 1,4-trans polymer in accordance with 1-dimensional pore geometry, while poly(acrylonitrile) (PAN) could be obtained as a stereoregular isotactic product by acrylonitrile polymerization in AV dipeptide. Finally, taking advantage of the dipeptide lability and unique thermal properties of poly(acrylonitrile), AV-PAN nanocomposites were used as a scaffold to obtain carbon replicas of the starting nanocomposite crystals (carbon micro-fibrils) showing anisotropic arrangement of the graphite domains.