Anionic Graft Copolymers with Poly(ethylene oxide) Side-Chains; Synthesis, Solution Properties and Ion Conduction
Sammanfattning: The research underlaying this thesis involves synthesis and characterization of well-defined anionic graft copolymers carrying poly(ethylene oxide) (PEO) side-chains. Two different grafting techniques were used. Backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene and an additional comonomer. Poly(ethylene oxide) monomethyl ether (MPEO) were grafted onto the backbone through reactions with the cyclic anhydride residues. The reaction rate was found to be dependent of both the neighbouring groups in the polymer backbone and the molecular weight of the MPEO. In the second method, polyamide 12 and poly(ethylene-co-vinyl alcohol) were used as backbone polymers. The amide and the hydroxyl groups were utilized as initiating sites for the anionic polymerization of ethylene oxide. The molecular weight of the grafts could be controlled by the ratios of the reactants used in the preparation. The PEO side-chains were endcapped by sulfonic acid groups, in a base-catalyzed ring-opening reaction between the hydroxyl groups and 1,3 propane sultone. The graft copolymers displayed a complex behavior in aqueous solution. Aggregation of these graft copolymers were strongly dependent on the salt concentration. Upon neutralization of the acid groups, typical polyelectrolyte behavior was experienced Single-ion conducting polymer electrolytes were obtained by doping the graft copolymers by alkali metal salts. Their ionic conductivity and dieletric properties were evaluated by impedance spectroscopy. The highest conductivity, 2'10-5 S/cm, at 80°C, was obtained for a rubberlike polymer with amorphous side-chains and sulfonic acid groups as anions. The fraction of ion pairs was found to increase with increasing temperature.
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