The basic method for synthesizing syndiotactic polystyrene-g-polybutadiene graft copolymers was investigated. First, the syndiotactic polystyrene copolymer, poly(styrene-co-4-methylstyrene), was prepared by the copolymerization of styrene and 4-methylstyrene monomer with a trichloro(pentamethyl cyclopentadienyl) titanium(IV)/modified methylaluminoxane system as a metallocene catalyst at 50 C. Then, the polymerization proceeded in an argon atmosphere at the ambient pressure, and after purification by extraction, the copolymer structure was confirmed with 1 H-NMR. Lastly, the copolymer was grafted with polybutadiene (a ready-made commercialized unsaturated elastomer) by anionic grafting reactions with a metallation reagent. In this step, poly(styreneco-4-methylstyrene) was deprotonated at the methyl group of 4-methylstyrene by butyl lithium and further reacted with polybutadiene to graft polybutadiene onto the deprotonated methyl of the poly(styrene-co-4-methylstyrene) backbone. After purification of the graft copolymer by Soxhlet extraction, the grafting reaction copolymer structure was confirmed with 1 H-NMR. These graft copolymers showed high melting temperatures (240-250 C) and were different from normal anionic styrene-butadiene copolymers because of the presence of crystalline syndiotactic polystyrene segments. Usually, highly syndiotactic polystyrene has a glass-transition temperature of 100 C and behaves like a glassy polymer (possessing brittle mechanical properties) at room temperature. Thus, the graft copolymer can be used as a compatibilizer in syndiotactic polystyrene blends to modify the mechanical properties to compensate for the glassy properties of pure syndiotactic polystyrene at room temperature.

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Abstract.A new synthesis route of phosphonated multi-block, branched copolyimide is proposed in this research. The synthesis and characterization of the series of new phosphonated graft copolyimides were prepared by combination of one-step high temperature polymerization and phosphonation method by lithiation and reaction with excess diethylchlorophosphate. The phosphonate ester product was converted to the phosphonic acid by hydrolysis. A branched polyimide structure was achieved by coupling the two polyimides with 3, 3'-diaminobenzidine. A phosphonated branched copolyimide with 32 % mol phosphonation exhibited high thermal stability, with a decomposition temperature in nitrogen of ~475°C. Proton exchange membranes prepared from these copolyimides had proton conductivity of 0.02 -0.03 S/cm at 100% humidity over a temperature range of 40 -100C.