Soft- and hard-segment phase segregation of polyester-based polyurethane

Polyester based polyurethanes were synthesized from 4,4 ' -methylene bis(phenyl isocyanate) (MDI) with butanediol as a chain extender and low molecular weight polyester-diol as a soft segment. Three polyesters were used in the synthesis of polyurethanes. Two of the polyesters, with molecular weight M-n = 2,660 and 2,155, were synthesized from adipic acid and 1,6-hexanediol, which had an even number of carbon atoms (polyester-6-6-1 and polyester-6-6-2). The other polyester with M-n = 2,770 was synthesized from pimelic acid and 1,5-pentanediol, which had an odd number of carbon atoms (polyester-7-5). Polyester-6-6-1 and polyester-6-6-2 consisting of even carbon monomers, had a higher degree of crystallinity at room temperature than polyester-7-5, which consists of an odd number of carbon monomers. The effect of polyester molecular weight and soft and hard-segmental geometric structure on the soft- and hard-segmental phase segregation was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and small angle X-ray scattering (SAXS).