L'objectif de ce travail de recherche est l'étude du transport des ions et des molécules d'eau à travers de membranes bicouche lipidique et des membranes polymériques. Dans une première partie, ce transport a été réalisé à travers des systèmes synthétiques auto-organisés, dont la sélectivité est en étroite relation avec le type d'architecture supramoléculaire formée grâce à des liaisons faibles. Le but est d'obtenir des systèmes qui peuvent imiter les fonctions de transport des protéines membranaires. Ce mimétisme fonctionnel est obtenu par l'auto-assemblage de molécules organiques contenant le cycle imidazole et la fonction urée, qui peuvent s'auto-assembler et créer des voies sélectives de transport des ions. Pour créer l'équivalent de la membrane cellulaire, nous avons utilisé des vésicules lipidiques unilamellaires. Ensuite, nous avons déterminé une relation entre l'activité des composés et leur structure. Pour ce faire, le transport des ions est étudié à l'aide d'une méthode de spectroscopie de fluorescence, et le transport d'eau par diffusion dynamique de la lumière utilisant la technique de « stopped flow ». Le but de la deuxième partie est la fabrication et la caractérisation des nouvelles membranes composites sous forme de couches minces, qui permettraient un bon compromis entre le flux d'eau et le rejet de sel. Dans ce cadre, la synthèse d'une série d'hydrazides en tant que précurseurs moléculaires a été réalisée, pour remplacer la métaphenylène diamine (MPD) classiquement utilisée. Ici aussi les liaisons hydrogène jouent un rôle important, car le principe de la séparation repose sur la création d'une organisation interne hautement réticulée. Les polymères synthétisés par polymérisation interfaciale ont été caractérisés par des méthodes de spectroscopie infrarouge, analyses thermogravimétriques et diffraction des rayons X. Les membranes composites ont été caractérisées par microscopie électronique à balayage, microscopie à force atomique et mesures d'angle de contact. Les performances membranaires ont été testées en filtration frontale d'eau et de solutions salines. / The aim of this work is the study of ion and water transport either across bilayer membranes or polymeric membranes used for reverse osmosis. In the first part, this transport through self-assembled synthetic systems was studied; the transport selectivity is in strong relation with the supramolecular structure, formed by weak intra and intermolecular bonds. Ion transport is studied by fluorescence spectroscopy and water transport is studied by light scattering using “stopped flow” technique. The objective is to obtain systems that could imitate transport functions of biomolecules as transmembrane proteins. This functional mimicry is achieved through self-assembly of organic molecules containing imidazole cycle and urea function that can self-assembly and form selective pathways for ion transport. To create the equivalent of the cell membrane, we used unilamellar lipid vesicles. Then, we determined a structure - transport activity relationship for a series of synthesized compounds. For the second part of this work we described the fabrication and the characterization of new thin film composite membranes for water desalination that can present a good balance between permeability and salt rejection. A series of hydrazides as molecular precursors was synthesized in order to replace the metaphenylene diamine (MPD), classically used. Again, hydrogen bonds play an important role, because the rejection is due to a high cross-linking. The polymers synthesized by interfacial polymerization were characterized by infrared spectroscopy, thermogravimetric analysis, and X-Ray diffraction. The membrane films were characterized by scanning electron microscopy, atomic force microscopy and contact angle measurements. Membrane performances were then tested in cross-flow filtration of water and saline solutions.

The present study in this thesis has attempted to resolve one of the key aspects of enhancing predictability of macroscopic behavior of Shape Memory Alloy (SMA) wire by considering variation of local phase inhomogeneity. Understanding of functional fatigue and its relation with the phase distribution and its passivation is the key towards tailoring thermal Shape Memory Alloy actuators’ properties and performance. Present work has been carried out in two associated areas. First part has covered solving a coupled thermo-mechanical boundary value problem where initial phase fractions are prescribed at the gauss points and subsequent evolution are tracked over the loading cycle. An incremental form of a phenomenological constitutive model has been incorporated in the modelling framework. Finite element convergence studies using both homogeneous and inhomogeneous SMA wires are performed. Effects of phase inhomogeneity are investigated for mechanical loading and thermo-electric loading. Phase inhomogeneity is simulated mainly due to process and handling quality. An example of mechanical boundary condition such as gripping indicates a negative residual strain at macroscopic behavior. Simulation accurately captures vanishing local phase inhomogeneity upon multiple cycles of thermo-mechanical loading on unconstrained straight SMA wire. In the second part, a phase identification and measurement scheme is proposed. It has been shown that by employing variation of electrical resistivity which distinctly varies with phase transformation, martensite phase volume fraction can be quantified in average sense over the length of a SMA wire. This can be easily achieved by using a simple thermo-mechanical characterization setup along with resistance measurement circuit. Local phase inhomogeneity is created in an experimental sample, which is subjected to electrical heating under constant mechanical bias load. The response shows relaxation of the initial shrinkage strain due to local phase. Results observed for thermo-electric loading on the inhomogeneous SMA wires compliment the results observed from the simulated loading cases. Several interesting features such as shrinkage of the inhomogeneous SMA wire after first loading cycle, relaxation of the residual strain over multiple loading cycles due to the presence of inhomogeneity are captured. This model promises useful applications of SMA wire in fatigue studies, SMA embedded composites and hybrid structures.