Synthesis and physical characterization of semi-IPNs of linear polyurethane and heterocyclic polymer network

Semi-interpenetrating polymer networks (semi-IPN) of linear polyurethane (L PU) and heterocyclic polymer network (HPN) were characterized by IR spectro scopy, small-angle X-ray scattering, differential calorimetry with diatherm al shells (temperature interval 130-500 K), and dynamic mechanical analysis (temperature interval 150-500 K and frequency range 0.3-30 Hz). The main r esults obtained may be summarized as follows: 1) The affinity of HPN toward s the soft LPU microphase is responsible for the absence of large-scale het erogeneity of semi-IPNs on their base (at least, at low HPN/LPU ratios). 2) Phenomenological analysis of small-scale, Arrhenius-like subglass relaxati ons (gamma(1) and gamma(2) in LPU and in HPN, respectively) revealed little interference of HPN with relaxation centers (RCs) of LPU in semi-IPNs, whi le the local environment of RCs in HPN, on the contrary, strongly depended on semi-IPN composition.