MORPHOLOGY DEVELOPMENT VIA REACTION-INDUCED PHASE-SEPARATION IN EPOXY POLY(ETHER SULFONE) BLENDS - MORPHOLOGY CONTROL USING POLY(ETHER SULFONE) WITH FUNCTIONAL END-GROUPS

Thermoset/thermoplastic blends, namely triglycidyl p-aminophenol/poly(ether sulfone) (epoxy/PES) systems, were cured using a curing agent, 4,4'-diaminodiphenylsulfone, and the morphology in the cured resins was observed by electron microscopy. In contrast to the spherical domain structure in a non-reactive PES system, a bicontinuous two-phase structure was obtained when reactive PES with amine chain ends was used. It suggests that the spinodal decomposition (SD) induced by the cure reaction is suppressed and structure coarsening is delayed by the in situ formation of PES-epoxy block copolymer, so that the phase-separated structure can be fixed at an early stage of SD. When a reactive PES was used, the periodic distance Lambda(m) of the bicontinuous structure was extremely small (Lambda(m) approximate to 20 nm). With the non-reactive PES in the blend, Lambda(m) increased from 20 nm to 1 mu m. In mixed PES systems, Lambda(m) can be reduced by the pre-reaction of PES with epoxy; e.g. from 0.7 mu m to 0.1 mu m for the 20:10 reactive/non-reactive system. Similar results were obtained for another reactive PES with hydroxyl chain ends.