Synthesis of thermoplastic poly(ester-siloxane)s in the melt and in solution

Abstract

Two series of thermoplastic elastomers, based on poly(dimethylsiloxane) PDMS, as the soft segment and poly(butylene terephthalate), PBT, as the hard segment, were synthesized by catalyzed transesterification, from dimethyl terephthalate, DMT, silanol-terminated poly(dimethylsiloxane), PDMS-OH Mn=1750g/mol, and 1,4-butanediol, BD. The mole ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 55:45. The first series was synthesized in order to determine the optimal mole ratio of BD and DMT for the synthesis of high molecular weight thermoplastic poly(ester-siloxane)s, TPESs. The second series was performed in the presence of the high-boiling solvent, 1,2,4-trichlorbenzene in order to increase the mixing between the extremely non-polar siloxane prepolymer and the polar reactants, DMT and BD, and, therefore, avoid phase separation during synthesis. The structure and composition of the synthesized poly(ester-siloxane)s were verified by 1H-NMR spectroscopy, while the melting temperatures and degree of crystallinity were determined by differential scanning calorimetry (DSC). The effectiveness of the incorporation of the silanol-terminated poly( dimethylsiloxane) into the polyester chains was verified by chloroform extraction. The rheological properties of the poly(ester-siloxane)s were investigated by dynamic mechanical spectroscopy (DMA).

Dve serije termoplastičnih elastomera na bazi poli(dimetilsiloksana) kao mekog segmenta i poli(butilentereftalata) kao tvrdog segmenta sintetisane su katalizovanom transesterifikacijom polazeći od dimetiltereftalata, DMT silanol-terminarnog poli(dimetil-siloksana), PDMS-OH, Mn=1750g/mol i 1,4-butandiola, BD. Molski odnos početnih komonomera odabran je tako da je rezultovao u konstantnom masenom odnosu tvrdih i mekih segmenata od 55:45. Prva serija je sintetisana sa ciljem da se odredi optimalan molski odnos komonomera BD i DMT za dobijanje termoplastičnih elastomera velikih molarnih masa. U drugoj seriji sinteze su izvođene u prisustvu teško isparljivog rastvarača 1,2,4-trihlorbenzena sa ciljem da se poveća mešljivost izuzetno nepolarnog poli(dimetilsiloksanskog)pretpolimera i polarnih reaktanata, kao što su DMT i BD i samim tim da se izbegne fazna separacija u reakcionoj smeši tokom sinteze. Struktura i sastav sintetisanih poli(estar-siloksana) potvrđeni su 1H-NMR spektroskopijom, dok su temperatura topljenja i stepen kristaliničnosti određeni diferencijalnom skenirajućom kalometrijom (DSC). Efikasnost ugradnje silanol-terminiranog poli(dimetilsiloksana) u poliestarske lance utvrđena je na osnovu ekstrakcije hloroformom. Reološka svojstva poli(estara-siloksana) ispitana su dinamičko-mehaničkom spektroskopijom.