The effect of segment length on some properties of thermoplastic poly(ester-siloxane)s

Abstract

A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two-step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl-terminated poly(dimethylsiloxane)s (M̄ n = 550-2170 g mol -1 ) with 1,4-butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester-siloxane)s were examined by 1 H NMR spectroscopy. The effectiveness of the incorporation of the methyl-ester-terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (T m and T g ) and the thermal and thermo-oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied.