Poly(imide–amide)–poly(ethylene adipate) hybrid networks. I. Nanostructure and segmental dynamics

Segmental dynamics at 200–500 K and nanometer-scale structure were studied by SAXS, DSC and creep rate spectroscopy (CRS) techniques in two series of poly(ethylene adipate)-crosslinked poly(imide–amide)s with regularly varied composition and different lengths of PEA crosslinks (Mn=1.300 and 2.700 g mol−1). The crystallization ability was observed in networks with longer PEA crosslinks. Shorter PEA crosslinks induced non-crystalline, nanostructured PIA–PEA networks. Combined DSC/CRS analysis indicated the pronounced heterogeneity of segmental dynamics in the latter networks. The wide dispersions of motional activation energies within the glass transitions were found by DSC, and manifestation of a few constituent segmental motions was shown in the creep rate spectra. The observed effects could be explained in terms of (i) the different constraining influence of PIA rigid constituents on dynamics in PEA crosslinks, and (ii) the breakdown of motional cooperativity as a result of loosening of PEA chain packing in presence of the PIA rigid nanodomains.