No description available.

L'élaboration de batteries performantes dans le but de promouvoir l’utilisation de véhicules électriques fait partie des stratégies majeures de développement durable. Les batteries constituées d’une électrode de lithium métallique semblent parmi les plus prometteuses. Cependant, cette technologie pose des problèmes de sécurité due à la croissance de dendrites. Afin de supprimer ce phénomène, des travaux sont consacrés à l’élaboration d’électrolytes polymères solides (SPE) combinant une conductivité ionique élevée et des propriétés mécaniques suffisantes pour empêcher cette croissance dendritique. Une des stratégies pour obtenir des SPE présentant l’ensemble des propriétés recherchées est l’élaboration de copolymères à blocs. Ainsi, un bloc POE assurant la conductivité ionique est combiné avec d’autres polymères aux propriétés mécaniques adaptées. À l’heure actuelle, quelques matériaux pourraient répondre à l’ensemble de ces critères, mais seulement à 80°C. L’objectif de cette thèse est de mettre au point un matériau avec de bonnes performances en termes de conductivité ionique et de tenue mécanique à 40 °C. Notre stratégie consiste à diminuer la cristallinité et la température de fusion du POE afin d’optimiser la conductivité à basse température. Plusieurs séries de copolymères à blocs à base de divers POE linéaires et de polymères anioniques ont été synthétisées par NMP. Les copolymères à blocs constitués d’un polycondensat de POE (Tf < 40°C) révèlent une conductivité ionique relativement élevée (1,3×10-6 S.cm-1) à 40°C couplée à une grande rigidité mécanique (Ey=50MPa). Ce nouveau matériau apparaît donc comme un SPE prometteur pour les batteries au lithium métallique. / The elaboration of efficient batteries to promote the use of electric vehicles is a matter of primary importance for sustainable long-term development. Lithium-Metal Batteries (LMB) are among the most promising. However, such technology presents several safety issues due to dendritic growth. To overcome these drawbacks, studies are performed on solid polymer electrolytes (SPE) that combine both high conductivity and suitable mechanical properties to prevent the dendritic growth. One of the strategies to obtain a SPE displaying all the desired properties is the elaboration of block copolymers. Like so, a PEO bloc with high ionic conductivity is combined with suitable mechanical properties of another polymer. Currently, many materials could meet the different requirements, but only at 80°C. The aim of this thesis is to develop a polymer material offering good performances in terms of ionic conductivity and mechanical rigidity at 40 °C in order to limit the energy loss. Our strategy consists in reducing the crystallinity and the melting temperature of PEO to optimize its conductivity at low temperature. In order to do so, several block copolymer sets constituted of various linear PEO and anionic polymers have been synthesized by NMP. Interestingly, the block copolymers containing PEO with a low degree of crystallinity, due to the limitation of chain stereoregularity, display low melting temperatures (Tf < 40°C). Moreover, the one made of polycondensats of PEO exhibits a relatively high ionic conductivity (1.3×10-6 S.cm-1) at 40 °C while displaying strong mechanical properties (Ey=50MPa). This new material seems to be a promising SPE for LMB.

A diblock copolymer of Poly (Styrene-b- [ethylene-co-propylene]) has been used as a stabilizer in non-aqueous dispersion polymerizations of methyl methacrylate and vinyl acetate in n-heptane. The particles thus produced were stabilized by well defined surface layers of ethylene-propylene copolymer chains. The dependence of the particle size on the stabilizer, monomer and initiator concentrations was studied. Both seeded and one-shot polymerization techniques were investigated. Polymer particles were characterized by transmission electron microscopy to determine particle shape and size. The long term stability of both types of polymer particles suggests that the anchoring efficiency in both systems was good. Rheological studies confirmed the sphericity of the particles and showed the particles to be non-flocculated under shear. The thickness of the surface layer was determined from viscosity studies of the dispersions at 298, 308 and 318K. Solution viscosities dispersions at of a narrow distribution standard of ethylene-propylene copolymer in n-heptane and in a binary liquid mixture of n-heptane and n-propanol (79:21, v/v) at 298, 308 and 318K were obtained in order to estimate the root-mean-square end-to-end distance of free ethylene-propylene copolymer chains. The thickness of the surface layer was observed to increase on raising the temperature and to decrease on changing the solvency of the dispersion medium from a good solvent to almost a theta solvent for the ethylene-propylene copolymer chains. The dimensions of the surface layer were slightly larger than the dimensions of the free ethylene-propylene copolymer chains in solution suggesting that long ethylene-propylene chains terminally anchored at the interface are only slightly extended over random coil dimensions. Calculations of the mean separation distance between adjacent stabilizing ethylene-propylene copolymer chains indicated close-packing of ethylene-propylene copolymer chains at the particle-liquid interface which may contribute to the slight extension of the ethylene-propylene copolymer chain conformation. The theta-conditions for ethylene-propylene copolymer in a mixture of n-heptane and n-propanol were determined using samples obtained by hydrogenating polyisoprene standards. The solvency of the dispersion medium for the stabilizing ethylene-propylene copolymer chain on the polymer particles was reduced until flocculation occurred, and this was achieved by cooling the dispersion system to find the critical flocculation temperature or by adding a non-solvent (n-propanol) for the ethylene-propylene copolymer chains at constant temperature to find the critical flocculation volume. The polymer dispersions just retained stability at theta conditions and started to lose stability when the dispersion medium was changed to slightly worse than a theta system for the ethylene-propylene chains. The close correspondence of the flocculation conditions to the theta conditions for free ethylene-propylene copolymer chains confirms that the steric stabilization mechanism is operative for these dispersions.

No description available.

No description available.

This thesis addresses three issues. These are the self-assembly of block copolymer in selective solvents, hierarchical assembly of micelles or crosslinked micelles of block copolymers, and the application of block copolymers as solid state compatibilizers in polymer-based photovoltaic cells. Poly(acrylic acid)-block-(2-cinnamoyloxylethyl methacrylate)-block-poly(perfluorooctylethyl methacrylate) or PAA-b-PCEMA-b-PFOEMA self-assembles in solvent mixtures of α,α,α-trifluorotoluene (TFT) and methanol, which are selective towards PAA. At TFT volume fraction (fTFT) of 40 %, the copolymer forms vesicles at 70 oC and cylinders at 21 oC. These two structures inter-convert via meta-stable intermediates including jellyfish-like, tethered vesicular, and bilayer sheet-like structures. These structures occur in kinetic experiments involving quick temperature swing from 21 to 70 oC or vice versa and also in experiments involving annealing samples long at temperatures between 21 to 70 oC. Thus, they are meta-stable and point to complex pathways for the morphological transition. At fTFT = 10 %, the polymer forms vesicles with bumpy surface at 70 oC and toroids with sharp angles at 21 oC. Closely examined is how the liquid crystalline nature of the PFOEMA block affects the formation of these unique morphologies and their morphological transitions. Two types of hierarchical assembly of cylindrical micelles (cylinders) or crosslinked cylindrical micelles (fibers) of block copolymers are examined. First, carboxyl-bearing nanofibers of PAA-b-PCEMA and amino-bearing nanocylinders from poly(tert-butyl acrylate)-block-poly(2-cinnamoyloxyethyl methacrylate)-block-poly(2-dimethylamino-ethylmethacrylate), PtBA-b-PCEMA-b-PDMAEMA, are mixed in solvent. The two species firstly aggregate via electrostatic interaction. Upon heating and aging, the cylinders dissociate on the fibers and eventually evolve into composite multilayered cylindrical structures. Second, layer-by-layer (LBL) deposition of carboxyl- and amine-bearing nanofibers yielded multilayer films. These films detached from a substrate separate nanospheres based on their size and surface charge differences. Diblock copolymers poly(3-hexylthiophene)-block-poly(2-cinnamoyloxyethyl methacrylate-random-2-[6,6]-phenyl-C61-butyroyoxyethyl methacrylate) (T-C60C) and poly(3-hexylthiophene)-block-poly(2-acetoxyethyl methacrylate-random-2-[6,6]-phenyl-C61-butyroyoxyethyl methacrylate) (T-C60A) are synthesized and used as compatibilizers for polymer-based photovoltaic cells containing poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Both copolymers can stabilize the morphology of the active layer and thus the device performance. T-C60A in the active layer yields longer life-times and better initial performance of the devices, due to the matching of surface tensions between C60A and PCBM. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-02-05 13:45:04.189

No description available.

No description available.

Research Doctorate - Doctor of Philosophy (PhD) / The adsorption characteristics of pH responsive tertiary amine methacrylate-based diblock copolymers have been investigated. The main focus of this work is on poly(2-(dimethylamino)ethyl methacrylate-b-poly(2-(diethylamino)ethyl methacrylate (PDMA-b-PDEA) adsorption to the silica/aqueous solution interface at pH 9. Differing degrees of polymerisation and quaternisation were investigated with some attention given to variation of the block hydrophobicity utilising poly(2-(dimethylamino)ethyl methacrylate-b-poly(2-(diisopropylamino)ethyl methacrylate (PDMA-b-PDPA). Principally, optical reflectometry (OR) and atomic force microscopy (AFM) have been employed to monitor the adsorption in terms of adsorbed mass and layer morphology. A variety of other techniques have been utilised to provide ancillary information, including quartz crystal microbalance, zeta potential, dynamic light scattering and contact angle measurements. The combined results have provided a comprehensive understanding of the adsorption characteristics for the copolymers studied. Micelles of the tertiary amine methacrylate-based copolymers adsorbed readily to silica from aqueous solution at pH 9. The adsorption isotherms were determined, exhibiting a high affinity Langmuirian shape where the CMC did not appear to impact on the adsorbed mass. The adsorption was rationalised by the interaction between the cationic PDMA corona of the micelles with the negatively charged substrate. The more hydrophobic PDEA core block increased the level of adsorption above that observed for the PDMA homopolymer. It was shown that the adsorbed layers were robust to rinsing with electrolyte at high pH, although reduction of the pH to 4 yielded significant desorption. The adsorbed layer morphology observed by in situ AFM exhibited distinct micellar structures. The combined adsorbed mass and AFM images showed a significantly higher surface aggregation number than the measured solution aggregation number, indicating a more complex adsorption process than simple direct micelle adsorption. The adsorption kinetics were studied to elucidate the adsorption mechanism and revealed complex dynamic processes. Particular focus was given to the adsorption of 0q PDMA93-b-PDEA24 where the impact of concentration was evident and three mechanistic regimes could be defined; below the CMC, just above the CMC and far above the CMC. Interestingly, the adsorption process just above the CMC indicates a surface aggregation mechanism, while well above the CMC, the adsorption proceeds via a process that includes both direct micelle and unimer adsorption. On longer timescales, the adsorption at higher concentrations revealed an additional induction period of micelle relaxation on the surface that allowed for further adsorption. Increasing the PDMA quaternisation was found to reduce post adsorption rearrangement and as result equilibrium was reached more quickly for the highly quaternised analogues. The response of the adsorbed PDMA-b-PDEA copolymer films to multiple changes in solution pH (9 and 4) was monitored. After the initial desorption of copolymer with rinsing at pH 9 and then at pH 4, the adsorbed mass of copolymer was found to be constant with multiple cycles of pH. The remaining robust adsorbed layers, then exhibited reversible uptake and release of water with multiple pH cycles as measured by QCM. This observation was readily rationalised by the observed changes in copolymer charge (and hence hydrophobicity) affecting the interaction of the copolymer chains with the surrounding solution. While these characteristics were found to be reversible with pH cycling it was found that the initial micelle structure of the adsorbed film was lost upon the first rinse to pH 4. Finally, the first low Tg micelle-micelle multilayers of up to six layers were constructed using alternating layers of cationic and anionic tertiary amine methacrylate-based copolymers at pH 9. The existence of true micellar structures within each layer was proven using in situ AFM imaging where the alternating layer characteristics were supported by measured force curves. The construction of the individual micelle layers was also monitored by OR, where clear evidence of layer build-up was shown. In addition, each layer was robust to rinsing with electrolyte at the adsorbing pH, although, the stability of the formed multilayer was found to be limited to six layers. Upon reduction of the pH, almost all the adsorbed material was instantaneously removed from the surface. The stimulus-responsive nature of such multilayer films augurs well for potential controlled uptake/release applications. These findings should greatly encourage a larger research focus on micelle-micelle multilayers.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 261-269). Available also in a digital version from Dissertation Abstracts.