Structure and dynamic/compositional heterogeneity in polycyanurate-poly(tetramethylene glycol) hybrid networks

Structure and dynamics over the range from -150 to 300 degrees C were studied in a series of polycyanurate-poly(tetramethylene glycol) (PCN-PTMG) hybrid networks. Wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS), laser-interferometric creep rate spectroscopy (CRS), differential scanning calorimetry (DSC), and thermally stimulated depolarization currents (TSDC) techniques were applied. The networks were synthesized from the dicyanate ester of bisphenol A (DCEBA) and hydroxyl-terminated PTMG with M-n = 1000, 2000 or 5000 g/mol and weight fraction of 10, 20, 30, and 40%. The noncrystalline structure and the pronounced structural nanoheterogeneity, depending on PTMG chain length and PCN-PTMG ratio in the hybrid systems, were evidenced. Combined CRS/DSC analysis revealed a complex dynamics in these networks, in particular a dispersion of glass transitions in a wide temperature range. On this basis, the presence of nanodomains with different degrees of rigid cross-linking (X-CN -> PCN), i.e., compositional nanoheterogeneity in these hybrids was shown. The results obtained turned out to be of applied interest because of a substantial increase in tensile strength because of arising microplasticity at low temperatures, and retaining some creep resistance, at low stresses, up to temperatures much higher the basic T-g.