Synthesis and characterization of thermoplastic poly(ester-siloxane)s

Two series of thermoplastic poly(ester-siloxane)s, based on poly(dimethylsi loxane) (PDMS) as the soft segment and poly(butylene terephthalate) as the hard segment, were synthesized by two-step catalyzed transesterification re actions in the melt. Incorporation of soft poly(dimethylsiloxane) segments into the copolyester backbone was accomplished in two different ways. The f irst series was prepared based on dimethyl terephthalate, 1,4-butanediol an d silanol-terminated poly(dimethylsiloxane) (PDMS-OH). For the second serie s, the PDMS-OH was replaced by methyl diesters of carboxypropyl-terminated poly(dimethylsiloxane)s. The syntheses were optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBU)(4)), and stabili zer, N,N'-diphenyl-p-phenylene-diamine, as well as the reaction time. The r eactions were followed by measuring the inherent viscosities of the reactio n mixture. The molecular structures of the synthesized poly(estersiloxane)s were verified by H-1 NMR spectroscopy, while their therm. al properties we re investigated sing differential scanning calorimetry. (C) 2001 Society of Chemical Industry.