Miscibility and morphologies of poly(arylene ether phenyl phosphine oxide/sulfone) copolymer/vinyl ester resin mixtures and their cured networks

Nonreactive bisphenol A-based poly(arylene ether triphenyl phosphine oxide/ diphenyl sulfone) statistical copolymers and a poly(arylene ether triphenyl phosphine oxide) homopolymer, each having a number-average molecular weigh t of about 20 kg/mol, were synthesized and solution-blended with a commerci al dimethacrylate vinyl ester resin. Free-radical cured systems produced mo rphologies that were a function of both the amount of phosphonyl groups and the weight percentage of the copolymers. For example, highly hydrogen-bond ed poly(arylene ether phenyl phosphine oxide) homopolymer/vinyl ester resin mixtures were homogeneous in all proportions both before and after the for mation of networks. Copolymers containing low amounts (less than or equal t o 30 mol %) of the phosphonyl groups displayed phase separation either befo re or during cure. The phase-separated cured materials generally had phase- inverted morphologies, such as a continuous thermoplastic copolymer phase a nd a particulate, discontinuous vinyl ester network phase, except for syste ms containing a very low copolymer content. The resin modified with a copol ymer containing 30 mol % phosphine oxide comonomer showed improved fracture toughness, suggesting the importance of both phase separation and good adh esion between the thermoplastic polymer and the crosslinked vinyl ester fil ler phase. The results suggested that the copolymers with high amounts of p hosphine oxide should be good candidates for interphase sizing materials be tween a vinyl ester matrix and high-modulus carbon fibers for advanced comp osite systems. Copolymers with low amounts of phosphonyl groups can produce tough, vinyl ester-reinforced plastics. The char yield increases with the concentration of bisphenol A poly(arylene ether phosphine oxide) content, s uggesting enhanced fire resistance. The incorporation of thermoplastic copo lymers sustains a high glass-transition temperature but does not significan tly affect the thermal degradation onset temperature. (C) 2000 John Wiley & Sons, Inc.