Properties of Polystyrene-Polydimethylsiloxane Block Copolymers
Block copolymers of polystyrene and polydimethyIsiloxane formed when hexamethylcyclotrisiloxane polymerized from the “living” ends of polystyryllithium. Little of the complicating intra- or intermolecular chain scission usually encountered in anionic siloxane polymerization occurred and essentially pure block copolymers were obtained. These were of the AB or BAB variety (where B signifies polydimethyIsiloxane and A polystyrene) depending on the functionality of the alkyllithium initiator used in formation of the polystyryHithium. The block copolymers, owing to the disparity in solubility between the A and B blocks, showed a tendency to form microphases in the bulk. The BAB block copolymers upon conversion to (BAB)X multi-block systems gave strong thermoplastic elastomers which could be deposited as films from solution or directly molded without any added re-enforcing fillers or cross-linking. Micro- phase formation was also observed in the multi-block copolymers.
KeywordsBlock Copolymer Yield Break Thermoplastic Elastomer Discontinuous Phase Selective Solvent
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