PHASE-BEHAVIOR IN COPOLYMER BLENDS OF POLY(P-CHLOROSTYRENE-CO-O-CHLOROSTYRENE) AND PHENYLSULFONYLATED POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE)

The miscibility of random copolymers of o-chlorostyrene and p -chloros tyrene [P (oClSt-co-pCISt)] with partially phenylsulfonylated poly(2,6 -dimethyl-1,4-phenylene oxide) (SPPO) copolymers has been studied, usi ng differential scanning calorimetry (DSC) to establish T(g) behavior. It already has been established that the isomeric effect of the chlor ine substitution on miscibility is large. Thus the para-chloro-substit uted styrenic homopolymer is miscible with all SPPOs containing more t han approximately 5 mol % phenylsulfonylation, whereas the ortho-chlor o-substituted homopolymer is immiscible with the entire range of SPPO copolymer compositions (and also with the respective homopolymers). As a result of this asymmetric behavior of the homopolymers, the width o f the window of miscibility in blends now investigated containing copo lymers with high pCISt content and SPPO is much greater than in the co rresponding blends containing copolymers with large mole fraction of o ClSt. These differences are reflected in the corresponding chi paramet ers calculated from analysis of the data. It was also found that the m iscibility is temperature dependent and that the regime in the copolym er-copolymer composition plane shrank as the equilibrium temperature i ncreased, results indicative of LCST behavior. (C) 1994 John Wiley & S ons, Inc.