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 -chlorostyrene [ P (oC1Stco-pC1St)] with partially phenylsulfonylated poly (2,6-dimethyl-1,4-phenylenoex ide)( SPPO) copolymers has been studied, using differential scanning calorimetry (DSC) toestablish Tg behavior. It already has been established that the isomeric effect of the chlorinesubstitution on miscibility is large. Thus the para-chloro-substituted styrenic homopolymeris miscible with all SPPOs containing more than - 5 mol % phenylsulfonylation, whereasthe ortho-chloro-substituted homopolymer is immiscible with the entire range of SPPOcopolymer compositions (and also with the respective homopolymers) . As a result of thisasymmetric behavior of the homopolymers, the width of the window of miscibility in blendsnow investigated containing copolymers with highpClSt content and SPPO is much greaterthan in the corresponding blends containing copolymers with large mole fraction of oC1St.These differences are reflected in the corresponding X parameters calculated from analysisof the data. It was also found that the miscibility is temperature dependent and that theregime in the copolymer-copolymer composition plane shrank as the equilibrium temperatureincreased, results indicative of LCST behavior