The number of peaks
corresponding to the crystalline regions is increased by adding the
diamine chain extender to the structure. The phase separation in
the PU2 sample is greater than that of the PU1 due to the existence
of more N–H groups, observed in the FTIR spectrum for the PU2
sample. When the hard and soft segments are separated from each
other, they are more likely regulated originally and can be located
in crystalline cells. Hence, the amount of crystallization is
increased in PU2 sample. In other words, the interference and
intermixture of phases will be increased due to the separation of
the hard and soft segments, and the synthesized polymer will
become more amorphous in the PU1 sample.