Abstract
Multiblock copolymers of styrene and propylene oxide were synthesized by coupling together polypropylene glycol and telechelic dihydroxyl polystyrene with 2,4-toluene diisocyanate (TDI) as the coupling agent. The results showed that it was better to terminate the telechelic dihydroxyl polystyrene with TDI first, then react with polypropylene glycol. The copolymer obtained in this two-step method possesses less homopolymers than that obtained when all the three reagents reacted together in one step. The crude product can be purified by extractions with absolute ethyl alcohol and decalin in order to remove the unreacted polypropylene glycol and polystyrene respectively. The purified products were characterized by IR, 1H NMR, GPC, membrane osmometry, elemental analysis, and shown to be multiblock copolymers of styrene and propylene oxide. The multiblock copolymer exhibits two glass transition temperatures (Tg) and behaves like a thermoplastic elastomer at 20—30% polystyrene content. Addition of 2% of the copolymers to the blends of polystyrene and epichlorohydrin rubber improves evidently their mechanical properties and causes the two Tg’s become closer.
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