초록
New types of polyurethane (PU) have been synthesized using 3,3'-dimethyldiphenyl 4,4'-diisocyanate (TODI) in order to test the effect of the chemical structure of hard segment on the domain/segment deformation behavior and mechanical stability of polyurethane. The effect of hard segment (H/S) content on the domain/segment deformation behavior was measured with SAXS and FTIR-dichroism methods. For TODI-based PU of low H/S content, the long axes of individual hard domains of lamellar type were aligned along the uniaxial stretching direction. When the hard segment content increases, the hard domains form lamellar stacks and those stacks are either rotated or tilted towards the initial stretching depending on their H/S content. For polyurethanes of highest HIS content, the selective domain break-up phenomenon was found to be a major restructuring process. Segmental orientation behavior observed with FTIR-dichroism is consistent with domain deformation behavior observed with SAXS. Compared with MDI-based polyurethane, TODI-based polyurethane exhibits better mechanical stability and this is explained in terms of the good packing behavior of hard segments in the TODI-based polyurethanes.