Morphology of polyurethanes with triol monomer crosslinked on hard segments

Polyester-based polyurethanes containing approximate to 60 wt % of polyeste r were synthesized from low molecular weight polyester (M-n approximate to 2000) and 4,4'-methylene bis(phenyl isocyanate) (MDI), with butanediol as a chain extender and glycerol as a crosslinker. The triol crosslinker was us ed in substitution for the 1,4-butanediol chain extender; thus, the crossli nker was chemical bonded to the hard segments of polyurethane. The morpholo gies of these polyurethanes were studied by differential scanning calorimet ry (DSC), small-angle X-ray scattering (SAXS), TMA (thermal mechanical anal ysis), and FTIR (Fourier transform infrared spectroscopy). Owing to the hig hly steric hindrance, the presence of triol crosslinker in the hard segment s resulted in a decrease in the aggregation of hard segments through hydrog en bonding. The experimental results revealed that the degree of phase segr egation of soft and hard segments decreased with increasing the triol cross linker content in the hard segments. (C) 1999 John Wiley & Sons, Inc.