| Abstract: | Poly(urethane‐siloxane) copolymers were prepared by copolymerization of OH‐terminated polydimethylsiloxane (PDMS), which was utilized as the soft segment, as well as 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (1,4‐BD), which were both hard segments. These copolymers exhibited almost complete phase separation between soft and hard segments, giving rise to a very simple material structure in this investigation. The thermal behavior of the amorphous hard segment of the copolymer with 62.3% hard‐segment content was examined by differential scanning calorimetry (DSC). Both the T1 temperature and the magnitude of the T1 endotherm increased linearly with the logarithmic annealing time at an annealing temperature of 100°C. The typical enthalpy of relaxation was attributed to the physical aging of the amorphous hard segment. The T1 endotherm shifted to high temperature until it merged with the T2 endotherm as the annealing temperature increased. Following annealing at 170°C for various periods, the DSC curves presented two endothermic regions. The first endotherm assigned as T2 was the result of the enthalpy relaxation of the hard segment. The second endothermic peak (T3) was caused by the hard‐segment crystal. The exothermic curves at an annealing temperature of above 150°C exhibited an exotherm caused by the T3 microcrystalline growth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5174–5183, 2006 |
