¡§Blue phase¡¨ LCD panels features the advantages of superior response times¡Bwide viewing angle and no requirement for alignment by rubbing greater than conventional LCD modes. Thus, recently several groups have been developed both scientific and technological interests in the blue phases. However, the blue phases only exist in the narrow temperature range, typically a few Kelvin below the phase transition temperature of materials, which has been a problem for practical applications such as fast light modulators or display. In this paper, we proposed polymer-stabilized liquid crystalline blue phase by photopolymerizing the monomers in the isotropic phase and discussed the theoretical model to describe the stability of the blue phases. The polymer networks play an important role in stabilizing a liquid crystal blue phase. The morphology of polymer network was determined by the process of polymerization condition, like exposure intensity and temperature. Moreover, scanning electron microscopy (SEM) images were used to understand directly the network structures and to find the regularity of temperature intervals. In the meantime, we successfully extended the temperature range of blue phase over 140oC under suitable conditions. Based on this research results, the different temperature interval properties of cholesteric blue phases will apply on various photoelectric elements in the future.

Cross-linked polymers are of great importance to industrial practice and theoretical studies. The unique network structures of these materials have endowed them with many superior properties. In this thesis, we study cross-linked polymers from both of experimental and theoretical sides, with an emphasis on the formation process and properties of the prepared networks. Two specific problems are investigated: development of polymer coatings over solid particles with in situ curing, and molecular dynamics (MD) study of network formation kinetics and structure-property relationship. In the study of polymer coating, a hot-melt coating process for solid particles is developed. Phenolic resin is used to coat the substrates and subsequently cured in situ. Among various processing parameters, temperature is found to play an especially important role in the coating performance. Higher temperature leads to stronger coating layers with better barrier properties, whereas lower temperature is preferable for better surface morphology. These two trends can be partially reconciled with ramping temperature profiles; however, the improvement is eventually limited by the rate of heat transfer. In MD study, the effects of precursor topology on the formation, structure and mechanical properties of polymer networks are studied. Cross-linked polymer networks are synthesized from three sets of precursors with varying chain length. Little difference is observed between these networks in typical properties including radial distribution function, overall statistics of network connectivity, and glass transition behaviors. The elastic modulus of the network is found to correlate strongly with the number of elastic strands in the network, except at the highly-cross-linked limit where substantial discrepancy is observed between networks from different precursors. Although these final networks contain a similar level of structural defects, the choice of precursor has a significant effect on the spatial distribution of the defects, which explains the precursor dependence of their mechanical property observed in the tensile test. / Thesis / Master of Applied Science (MASc)

RM257 is a photopolymerisable diacrylate mesogen. In its normal way, the polymerization of the diacrylate mesogen is initiated by using UV light. RM257 mesogen have photopolymeriable acrylate endgroups. RM257 molecules form to polymer network. In this study, we use 632.8 nm HeNe laser to initiate the monomer conversion of RM257. The effects of light intensity, exposure time and temperature of monomer on the rate of polymerization have been studied. The monomer conversion of RM257 is found to have a higher rate when the mesogen in the isotropic phase. On other hand, using a two ¡Vbeen interference pattern, a periodic structure was be produced in the RM257 polymer network. The mesogen has a uniform ordered. To discuss that diacylate effected by holographic light field.

No description available.

Bulk imprinted polymers were synthesized using traditional small molecular weight imprinting techniques for the recognition of bovine serum albumin (BSA). Reproducibility and capacity concerns prompted the use of circular dichroism to investigate the potential effects that conditions commonly employed have on the structure of the protein prior to polymerization. These studies clearly showed a substantial change in the secondary structure of three common model protein templates when in the presence of various monomers and crosslinkers. Molecular docking was used to further examine the interactions taking place at the molecular level. Docking simulations revealed that significant amounts of non-covalent interactions are occurring between the amino acid side chains and ligands; although, the interactions taking place amongst the analyte and polypeptide backbone are responsible for the experimentally observed conformational change. The computational studies also showed that several of the ligands preferentially ‘docked’ to the same amino acids in the protein, indicating that if multiple monomers are employed, this competition for similar binding sites will potentially result in non-specific recognition. These findings are important as they offer insight into the fundamental reasons why recognition of macromolecular templates has proven difficult as well as provide guidance for future success in the field. Using this information, novel surface imprinted polymers were synthesized via a facile technique for the specific recognition of BSA. Thin films based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) as the functional monomer and varying amounts of either N,N’ methylenebisacrylamide (MBA) or poly(ethylene glycol) (400) dimethacrylate (PEG400DMA) as crosslinker were synthesized via UV free-radical polymerization. A clear and reproducible increase in recognition of the template was demonstrated for these systems as 1.6-2.5 times more BSA was recognized by the MIP sample relative to the control polymers. Additionally, these polymers exhibited specific recognition of the template relative to similar competitor proteins with up to 2.9 times more BSA adsorbed than either glucose oxidase or bovine hemoglobin. These synthetic antibody mimics hold significant promise as the next generation of robust recognition elements in a wide range of bioassay and biosensor applications. / text

Interest in microemulsions as potential platforms for polymerization stems from the wide range of phase behaviour dependant morphologies and domain sizes that can be generated in a low viscosity environment. By introducing polymerizable components into the oil and aqueous phases of a microemulsion, we may essentially create a low viscosity, low interfacial tension, bicontinuous template with nanostructured morphologies and narrow domain size distributions analogous to those generated through conventional interpenetrating polymer network (IPN) synthesis and spinodal decomposition. The main objective of this dissertation is to test the application of bicontinuous microemulsion templates to the formulation and polymerization of a silicone-hydrogel IPN. In addition, the project expands on the classical definition of IPNs to a scale of entanglement at the level of groups of polymer chains, as opposed to molecular or chain-level entanglement. This study is divided into two main parts. In the first part, silicone microemulsions were developed and characterized according to the Hydrophilic-Lipophilic Difference (HLD) framework. The hydrophobicity of silicone oils, the characteristic curvature of silicone surfactants and the co-surfactant contribution of methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) were quantified. These findings led to the successful formulation of bicontinuous microemulsions (μEs) containing silicone oil, silicone alkyl polyether and reactive monomers in aqueous solution. Ternary phase diagrams of these systems revealed the potential for silicone-containing polymer composites with bicontinuous morphologies. In the second part of this study, the formulation and simultaneous polymerization of polydimethylsiloxane-poly(methacrylic acid – hydroxyethyl methacrylate), (PDMS-P(MAA-HEMA) IPNs from bicontinuous microemulsions was demonstrated. Laser scanning confocal microscopy (LSCM) on swollen polymers highlights aqueous pathways, and indicates the formation of bicontinuous morphologies with domain sizes at equilibrium swelling ranging from ~100 nm to 1 μm. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization. The process developed demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.

Interest in microemulsions as potential platforms for polymerization stems from the wide range of phase behaviour dependant morphologies and domain sizes that can be generated in a low viscosity environment. By introducing polymerizable components into the oil and aqueous phases of a microemulsion, we may essentially create a low viscosity, low interfacial tension, bicontinuous template with nanostructured morphologies and narrow domain size distributions analogous to those generated through conventional interpenetrating polymer network (IPN) synthesis and spinodal decomposition. The main objective of this dissertation is to test the application of bicontinuous microemulsion templates to the formulation and polymerization of a silicone-hydrogel IPN. In addition, the project expands on the classical definition of IPNs to a scale of entanglement at the level of groups of polymer chains, as opposed to molecular or chain-level entanglement. This study is divided into two main parts. In the first part, silicone microemulsions were developed and characterized according to the Hydrophilic-Lipophilic Difference (HLD) framework. The hydrophobicity of silicone oils, the characteristic curvature of silicone surfactants and the co-surfactant contribution of methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) were quantified. These findings led to the successful formulation of bicontinuous microemulsions (μEs) containing silicone oil, silicone alkyl polyether and reactive monomers in aqueous solution. Ternary phase diagrams of these systems revealed the potential for silicone-containing polymer composites with bicontinuous morphologies. In the second part of this study, the formulation and simultaneous polymerization of polydimethylsiloxane-poly(methacrylic acid – hydroxyethyl methacrylate), (PDMS-P(MAA-HEMA) IPNs from bicontinuous microemulsions was demonstrated. Laser scanning confocal microscopy (LSCM) on swollen polymers highlights aqueous pathways, and indicates the formation of bicontinuous morphologies with domain sizes at equilibrium swelling ranging from ~100 nm to 1 μm. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization. The process developed demonstrates a simple, single-step polymerization approach to forming IPNs from low viscosity microemulsion templates, and could potentially be extended to a variety of hydrophilic and hydrophobic monomers.

L’objectif de cette thèse était de réaliser de nouveaux matériaux à émissivité variable dans l’infrarouge pour une application de régulation thermique des satellites artificiels. Dans ce contexte, l’étude s’est concentrée sur l’élaboration et la caractérisation de dispositifs électroémissifs à base d’un polymère conducteur électronique, le poly(3,4-éthylènedioxythiophène) (PEDOT) obtenu par électropolymérisation. Ces dispositifs électroémissifs ont ensuite été évalués dans des conditions partiellement représentatives de l’environnement spatial.La première partie de ce manuscrit a été consacrée à l’incorporation du PEDOT par électropolymérisation au sein d’une matrice hôte, formée à partir d’un réseau interpénétré de polymère (RIP) à base de caoutchouc nitrile (NBR) et de poly(oxyde d’éthylène) (POE). L’électropolymérisation par une méthode de chronopotentiométrie pulsée a permis d’obtenir des couches actives de PEDOT reproductibles, démontrant ainsi que le procédé électrochimique est bien contrôlé. En parallèle, des dispositifs électroémissifs de référence dont la couche active de PEDOT a été synthétisée par une polymérisation chimique oxydante, ont été élaborés. Le comportement électrochimique, les propriétés optiques dans l’infrarouge et la morphologie des couches actives obtenues par électropolymérisation ont été comparés à celles obtenues par une polymérisation chimique oxydante. Une répartition différente du PEDOT en fonction de la méthode d’incorporation a notamment été démontrée.Dans la deuxième partie de ce manuscrit, le comportement actionneur des dispositifs électroémissifs, qui est majoritairement induit par une insertion ou une expulsion d’ions au cours du procédé redox, a été étudié. Un screening de liquides ioniques, possédant des structures chimiques différentes, a été réalisé. Le mécanisme d’ion impliqué lors de la réaction redox a été identifié par une méthode simple consistant à observer la variation de volume de la couche active de PEDOT. Cette méthode a permis de souligner le rôle prédominant des cations au sein du procédé redox. L’utilisation de deux liquides ioniques a notamment permis une réduction significative de la déformation du dispositif électroémissif de référence tout en conservant de bonnes propriétés optiques dans l’infrarouge. Des mélanges de liquides ionique et de sel de lithium ont également été étudiés. En fonction de la concentration en sel de lithium au sein d’un liquide ionique, il est possible de contrôler le mécanisme ionique qui gouverne la réaction redox. Une concentration en sel en particulier entraine à la succession des deux mécanismes ioniques, ce qui donne lieu à un faible effet actionneur tout en préservant l’électro-activité et les propriétés optiques dans l’infrarouge du système.Dans la dernière partie de ce manuscrit, un prototype a été réalisé et évalué pour une application de contrôle thermique. Des radiateurs à base de dispositifs électroémissifs ont été fabriqués puis testés dans des conditions proches de l’environnement spatial. Ces radiateurs ont ensuite été comparés à la technologie actuellement utilisée sur les satellites artificiels, les réflecteurs optiques solaires. Des changements de température significatifs (12 °C) ont été mis en évidence, démontrant la pertinence de ce type de système pour une application de régulation thermique. Une faible consommation électrique de ces systèmes a été mise en avant au cours de ces travaux. Associé à la faible masse embarquée les dispositifs électroémissifs élaborés ont ainsi un intérêt double pour l’application visée par rapport à la technologie actuelle. / The aim of this PhD work is to design new coatings with variable emissivity in the infrared for an application of thermal regulation of artificial satellites. In this context, the study focuses on the development of electroemissive devices based on an electronically conducting polymer, the poly (3,4-ethylenedioxythiophene) (PEDOT). These electroemissive devices are then evaluated under space like environment.The first part of this manuscript was devoted to the incorporation of PEDOT by electropolymerization within a host matrix based on an interpenetrating polymer network (IPN) including nitrile butadiene rubber (NBR) and poly (ethylene oxide) (PEO). Electropolymerization by a pulsed chronopotentiometry method resulted in reproducible active PEDOT layers, demonstrating that the electrochemical process is well-controlled. In parallel, electroemissive deviceswhose active layer of PEDOT was synthesized by an oxidative chemical polymerization, were elaborated as refernce devices. The electrochemical behavior, the infrared optical properties and the morphology of the active layers obtained by electropolymerization were compared with those obtained by an oxidative chemical polymerization. In particular, different distribution of PEDOT according to the incorporation method was demonstrated.In the second part of this manuscript, the actuator behavior of electroemissive devices, that is predominantly induced by insertion or expulsion of ions during the redox process, was studied. A screening of ionic liquids with different chemical structures was carried out. The ion mechanism involved during the redox process was identified by a simple method consisting in observing the volume variation of the PEDOT active layer. This method highlighted the predominant role of cations in the redox process. The use of two ionic liquids allowed a considerable reduction of the actuator behavior of a reference electroemissive device while maintaining high optical properties in the infrared. Mixtures of ionic liquids and lithium salt were also studied. Depending on the lithium salt concentration, the possibility of controlling the ionic mechanism that governs the redox reaction was underlined. A salt concentration in particular leads to the succession of the two ionic mechanisms and results in a low actuator behavior while preserving the electro-activity and the optical properties of the system.In the last part of this manuscript, a prototype was evaluated for a thermal control application. Radiators based on electroemissive devices were fabricated and tested under conditions close to the space environment. These radiators were then compared to the technology currently used on artificial satellites, optical solar reflectors. Significant temperature changes (12 °C) were demonstrated, proving the relevance of this type of system for the thermal regulation of satellites. In addition, a low electrical consumption of these systems was highlighted during this work. Associated to a reduced on-board weight, the electroemissive devices designed at the LPPI, have thus a double interest for the intended application with respect to the current technology.

Silicone hydrogels are receiving considerable interest due to their important biomedical application areas such as contact lenses and wound dressings. The applications of such materials are usually in the hydrated state, as hydrogels. However, manufacturing and molding processes are mostly carried out in the organically solvated state, as organogels. This thesis investigates the effects of some of the manufacturing parameters such as curing time and thermal processing on thermal, mechanical, viscoelastic and adhesive/cohesive fracture properties of silicone semi-interpenetrating polymer network organogels. Curing time may affect the extent of reaction and the crosslink density of a gel network. In order to investigate the effect of this parameter, materials were photo-cured for different times within the range of 150s to 1800s. Gel content, uniaxial tensile, dynamic mechanical, adhesive fracture and cohesive fracture properties were obtained as a function of photo-curing time and results were correlated with each other in order to have a better understanding of the effects on the material properties. Additionally, thermal properties of the gels were studied in detail. Crystallization and melting behavior of one of the solvents in the organogel were investigated by differential scanning calorimetry and thermal optical microscopy. Correlation between the thermal properties of the solvent and the gel network structure was shown. Dynamic mechanical analysis experiments were performed to investigate the effect of solvent crystallization on the mechanical properties. Finally, the effect of thermal processing parameters such as the heating  rate and the minimum cooling temperatures on the crystallization and the thermo-mechanical properties were studied. / Master of Science

Entangled semiflexible polymer networks are usually described by the tube model, although this concept has not been able to explain all experimental observations. One of its major shortcomings is neglecting the thermal fluctuations of the polymers surrounding the examined test filament, such that disentanglement effects are not captured. In this study, we present experimental evidence that correlated constraint release which has been predicted theoretically occurs in entangled, but not in crosslinked semiflexible polymer networks. By tracking single semiflexible DNA nanotubes embedded both in entangled and crosslinked F-actin networks, we observed different reptation dynamics in both systems, emphasizing the need for a revision of the classical tube theory for entangled polymer solutions.