Phase segregation of crosslinked polyurethane by small angle x-ray scattering

Abstract

Polyester based polyurethanes were synthesized from a low molecular weight polyester (Mn approx. 2000) and 4,4′-methylene bis(phenyl isocyanate) (MDI) with butanediol as a chain extender and glycerol as crosslinker. The polyester was synthesized from adipic acid and glycol, a mixture of 1,6-hexanediol and 1,2-propanediol. The effect of the crosslinker content on the phase segregation of soft- and hard-segments was studied by DSC (differential scanning calorimetry) and SAXS (small angle X-ray scattering). The introducing of triol functional group into the hard segments increased the aggregation of hard segments through crosslink covalent bonds. Owing to highly steric hindrance, the presence of tri-ol crosslinker in the hard segments decreased the aggregation of hard segments through hydrogen bonding. The phase segregation of soft- and hard- segments is thus due to the aggregation of hard-segments through crosslinked covalent bonds and H-bonding.