Block copolymer of trans-polyisoprene and urethane segment:: Crystallization behavior and morphology

A new type of urethane segmented copolymer was prepared from hydroxyl-terminated trans-polyisoprene (HTTPI) and toluene diisocyanate (TDI). The structures of the copolymer were characterized by FTIR and GPC. Crystalline properties of trans-polyisoprene (TPI) segments were investigated using WAXD and DSC techniques. The crystals of TPI segments are inclined to exist in low-melting form (LM). The melting temperature of TPI shifts to a lower temperature as the urethane segment was introduced. DMA studies show that, when TPI crystals were at the melting state, the storage modulus of the copolymer depended on the content of urethane segment. The hard segment here serves as physical crosslinkage. Nonisothermal crystallization kinetics of TPI segment was studied on the basis of the Ozawa equation. It was found that the hard segment suppresses the crystallization of the TPI segment. Morphology of two-phase separation was observed in the copolymer by SEM. (C) 2004 Wiley Periodicals, Inc.