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

Abstract

Two series of thermoplastic poly (ester-siloxane)s, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) as the hard segment, were synthesized by two-step catalyzed transesterification reactions in the melt. Incorporation of soft poly(dimethylsiloxane) segments into the copolyester backbone was accomplished in two different ways. The first series was prepared based on dimethyl terephthalate, 1,4-butanediol and silanol-terminated poly(dimethylsiloxane) (PDMS-OH). For the second series, 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 stabilizer, N,N′-diphenyl-p-phenylene-diamine, as well as the reaction time. The reactions were followed by measuring the inherent viscosities of the reaction mixture. The molecular structures of the synthesized poly(ester-siloxane)s were verified by 1H NMR spectroscopy, while their thermal properties were investigated using differential scanning calorimetry.