La «chimie verte » comprend le développement de procédés de synthèse respectueux de l'environnement, en réduisant notamment l'usage de solvants organiques. Dans ce but, nous avons montré qu'il était possible de synthétiser, à partir de microémulsions, des matériaux conducteurs protoniques, de structure prédéfinie, sans l'usage d'un autre solvant que l'eau.La première partie de cette étude a permis de démontrer la faisabilité de ce procédé. Le système ternaire choisi est composé d'une solution aqueuse d'acide 2-acrylamido-2-méthylpropane sulfonique (AMPS), de méthacrylate d'hexyle (HMA) comme phase hydrophobe et du tensioactif, le Brij® 35. Les structures des microémulsions ont été identifiées, selon leur composition, à partir de mesures de conductivité, de viscosité et d'imagerie par microscopies optique et confocale. Ces structures peuvent être inverse, lamellaire, bicontinue et directe. La polymérisation/réticulation par voie radicalaire des monomères présents dans les différentes phases conduit à des matériaux présentant ces mêmes structures. Les polymères étant réticulés, ces matériaux sont des réseaux interpénétrés de polymères (RIP).La seconde partie de cette étude a été consacrée à l'optimisation de la formulation des microémulsions pour obtenir des matériaux aux propriétés souhaitées. Ainsi, la fraction soluble et le taux de gonflement dans l'eau ont été considérablement réduits, tout en conservant une conductivité protonique de l'ordre de 10-3 S.cm-1. Les meilleurs résultats ont été obtenus en synthétisant un « double RIP », c'est-à-dire un RIP dans chacune des phases, matériau tout à fait original à ce jour. / "Green chemistry" includes the development of synthetic methods respectful of the environment, including reducing the use of organic solvents. For this purpose, we have shown that it is possible to synthesize, from microemulsions, proton conductive materials, predefined structure, without the use of a solvent other than water. The first part of this study demonstrates the feasibility of this method. The ternary system is selected from an aqueous solution consisting of 2-acrylamido-2-methylpropane sulphonic acid (AMPS), hexyl methacrylate (HMA) as hydrophobic phase and the surfactant, Brij® 35. The structures of microemulsions have been identified, depending on their composition from measurements of conductivity, viscosity and imaging optical and confocal microscopies. These structures can be inverse, lamellar, bicontinuous and direct. The polymerization/crosslinking of the monomers by free radical present in the various phases leads to materials having the same structures. Being crosslinked polymers, these materials are interpenetrating polymers networks (IPN). The second part of this study has been devoted to the optimization of the formulation of microemulsions to obtain materials with desired properties. Thus, the soluble fraction and the degree of swelling in water were significantly reduced, while maintaining proton conductivity of the order of 10-3 S.cm-1. The best results were obtained by synthesizing a "double IPN", that is to say, an IPN in each phase, entirely original material.

Many important therapeutic agents are associated with significant undesired side effects which often limit treatment duration and dosing. Specifically, most major classes of antitumor chemotherapeutics have deleterious effects on cell division and DNA synthesis throughout the body due to systemic biodistribution. Engineering systems for controlled drug delivery allows for improved quality of life during treatment; as well as higher localized therapeutic concentrations by isolating toxic drugs used in many diseases to specific physiological compartments. An important drug delivery strategy for controlled release of therapeutics is based on responsive polymer matrices, which undergo swelling transitions in response to environmental stimuli. Biologically relevant factors which may trigger the release of therapeutics from responsive polymers include pH, ionic strength, and temperature. Temperature responsive polymers integrated into a composite system with metal nanoparticles allow for on demand drug release via an externally-applied optical or magnetic energy source. The intent of this work was to develop a temperature-responsive drug delivery platform for controlled therapeutic release, as well to expand the toolbox for rational design of responsive hydrogel nanoparticles intended for therapeutic delivery. Temperature-responsive hydrogels were synthesized and examined in the form of nanoparticles and bulk polymer networks. These materials are based on interpenetrating polymer networks (IPNs) of polyacrylamide (PAAm) and poly(acrylic acid) (PAA), which exhibit a positive volume swelling response with respect to temperature. Since this system responds to pH, ionic strength, and temperature, these IPNs were characterized over a wide range of solution conditions. Critical synthesis parameters needed to optimize thermal responses for specific solution conditions were identified, as were the specific effects of pH and ionic strength on network swelling and stability. The reverse emulsion process used to synthesize IPN nanoparticles was characterized to determine how particle growth proceeds during preparation. To enhance biocompatibility, IPN nanoparticles were surface-modified with a corona of poly(ethylene glycol) to reduce protein adsorption, a common strategy to improve in vivo performance. Due to the large amounts of surfactants employed in the preparation of IPN nanoparticles, purification methods needed to improve safety of IPN nanoparticles were optimized, and studied in vitro to ensure cellular compatibility. / text

The objective of this work is to characterize and understand structure- mechanical property relationships in (meth)acrylate networks. The networks are synthesized from mono-functional (meth)acrylates with systematically varying sidegroup structure and multi-functional crosslinkers with varying mole fraction and functionality. Fundamental trends are established between the network chemical structure, crosslink density, glass transition temperature, rubbery modulus, failure strain, and toughness. The glass transition temperature of the networks ranged from -29 to 112 °C, and the rubbery modulus ranged from 2.8 to 129.5 MPa. At low crosslink density (Er < 10 MPa) network chemistry has a profound effect on network toughness. At high crosslink densities (Er > 10 MPa), network chemistry has little influence on material toughness. The characteristic ratio of the mono-functional (meth)acrylates components is unable to predict trends in thermoset toughness as a function of chemical structure, as is accomplished for thermoplastics. The cohesive energy density is a better tool for prediction of network mechanical properties. Due to superior mechanical properties, networks with phenyl ring sidegroups are further investigated to understand the effect of phenyl ring distance on toughness. This work provides a fundamental basis for designing (meth)acrylate shape memory polymer networks with specific failure strain, toughness, glass transition temperature, and rubbery modulus.

Thesis (Ph. D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Karl I. Jacob; Committee Member: Anselm C. Griffin; Committee Member: C. P. Wong; Committee Member: Rina Tannenbaum; Committee Member: William J. Koros; Committee Member: Yonathan S. Thio.

Les gels de fibrine présentent un fort intérêt en médecine régénérative, puisqu’ils miment la matrice temporaire créée lors de la cicatrisation. Cependant, quand préparés à concentration physiologique, ils ne sont pas manipulables, ni conservables à sec. Pour contrer ces désavantages, ils peuvent être associés à un autre réseau de polymères, dans une architecture de Réseaux Interpénétrés de Polymères (RIP). Cette approche a été utilisée pour associer à un réseau de fibrine, un coréseau semi-synthétique d’albumine de sérum bovin (BSA) et de poly(oxyde d’éthylène) (POE), obtenu par photopolymérisation de BSA et PEG modifiés avec des fonctions méthacrylate (BSAm, PEGDM).Il a été démontré par des tests ex vivo et in vitro que ces matériaux ont de multiples applications potentielles, puisqu’ils supportent à leur surface, la croissance de nombreux types cellulaires. De plus, il a été observé que ces matériaux peuvent servir comme vecteurs pour la délivrance de molécules d’intérêt thérapeutique.La technologie a d’ailleurs été optimisée, en utilisant non plus des précurseurs modifiés avec des fonctions méthacrylate, mais acrylate. Cette modification a permis de réduire la toxicité du procédé de synthèse, tout en conservant les performances des matériaux. Il a également été démontré que divers matériaux optimisés ont des mécanismes de dégradation différents, et contrôlables par leur formulation initiale.Enfin, deux nouvelles familles de RIPs à base de fibrine ont été développées, en associant à un réseau de fibrine, un autre réseau de protéine, la fibroïne de soie. Des RIPs parfaitement manipulables ont été obtenus, supportant à leur surface la culture de fibroblastes. Ces matériaux sont donc prometteurs pour l’ingénierie tissulaire de la peau et d’autres applications. / Fibrin gels are of interest in regenerative medicine, as they mimic the provisory matrix synthesized during wound healing process. However, when prepared at physiologic concentration, these gels cannot be handled, nor stocked in dry state. To face these drawbacks, they can be associated with another polymer network, in an Interpenetrating Polymer Network (IPN). This strategy was used to associate to a fibrin network, a semi-synthetic conetwork composed of bovine serum albumin (BSA) and poly(ethylene oxide) (PEO), obtained by photopolymerization of methacrylate-modified BSA and PEG.It was demonstrated through ex vivo and in in vitro experiments that these materials have numerous potential applications, as they support on their surface, the culture of numerous cell types. Moreover, it was observed that they may be used as drug carrier for drug release applications.Moreover, the technology was optimized by modifying the methacrylate functions on the precursors for acrylate functions. This modification allowed to reduce the toxicity of the process, while preserving materials performances. It was also demonstrated that these optimized materials have different degradation mechanisms, which are controllable by their initial formulation.Finally, 2 new groups of fibrin-based IPNs were developed, by associating to a fibrin network, another protein network, the silk fibroin. Perfectly handable IPNs were obtained, which support on their surface the culture of fibroblasts. These materials are then very promising for skin tissue engineering, and most likely other applications.

This diploma thesis deals with the influence of long term thermal load on the stability of high-viscous resins used for dental composites matrix. The process of polymerization was also investigated in connection with type and ratio of monomer units, mass content of the initiator system and the presence of nanosilica filler. Prepared resins were characterized by differential compensation photocalorimetry (DPC) and dynamic mechanical analysis (DMA). The dependence of the heat flow on time was measured by DPC. Based on the experimental data, the dependence of conversion on time and the dependence of polymerization rate on conversion were determined. Viscoelastic properties of the cured resins were determined by DMA. Experimentally measured data implies that by the influence of elevated temperature both the degree of conversion and the polymerization rate decreased. With a higher content of the initiator system incorporated in resin the decrease was more significant. Therefore, we can conclude that when the resin was exposed to the elevated temperature one of the components of the initiator system was inactivated. For the photopolymerized resins presence of two glass transition temperatures is typical due to the inhomogenous morphology of the cured resin. There are two types of domains with varying relative composition. However, after the degradation only one glass transition temperature was detected. That was caused by reducing the resin viscosity due to the increased temperature. Higher mobility of the initiator system molecules and monomers itself resulted in more homogenous structure of the cured resin. In case of elevated temperature exposed resins more significant decrease of the elastic modulus was observed. The curing process is considerably influenced by the type and ratio of the monomer units and by the presence of filler.

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