Modulated differential scanning calorimetry: 13. Analysis of morphology ofpoly(ethyl methacrylate) polyurethane interpenetrating polymer networks

The phase structure of poly(ethyl methacrylate)-polyurethane (PEMA/PUR) int erpenetrating polymer networks (IPNs) has been investigated by means of mod ulated-temperature differential scanning calorimetry (M-TDSC), dynamic mech anical thermal analysis (DMTA) and small-angle X-ray scattering (SAXS). Exp erimental data from both M-TDSC and SAXS indicate that the morphologies of all the PEMA/PUR IPN samples (90 : 10 to 10 : 90 PUR/PEMA) are multi-phase structures. The scattering peaks from SAXS are quite broad, thereby indicat ing a distribution of microdomain sizes from 5 to 12 nm. This structure for mation in IPNs is a competitive process between phase separation and the fo rmation of cross-links which restricts segmental diffusion. An M-TDSC-based characterization method for IPNs has been developed using the differential of heat capacity signal, dC(p)/dT, to analyze phase structure and calculat e the weight fraction of each component. (C) 1998 Elsevier Science B.V. All rights reserved.