Characteristics of the phase transition of poly(siloxane/ether urethane) copolymers

The aim of this study is to investigate the characteristics of the phase transition for poly(siloxane/ether urethane) copolymers (PSi-EUs) consisting of PTMG/PDMS mixed soft segments and urethane hard segments by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). PSi-EUs exhibit three regions of amorphous phase transition, involving the PDMS soft phase, the PTMG soft phase and the urethane hard phase; therefore, they display phase separation due to low miscibility. Intermolecular hydrogen bonding, which is key to phase mixing, hence resulting in a low degree of phase separation, occurs between the PTMG soft segments in the PTMG/PDMS mixed soft phase and the urethane hard segments. Accordingly, the PSi-EUs are superior to poly(siloxane urethane) copolymer (PSiU) in terms of tensile strength due to the low phase separation and strain-induced crystallization resulting from PTMG soft segments.