Miscibility in blends of sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly( p ‐bromostyrene‐ co ‐ o ‐bromostyrene)

Miscibility in blends of random copolymers of p ‐bromostyrene ( p BrSt) and o ‐bromostyrene ( o BrSt) [P( p BrSt‐ co ‐ o BrSt)] with partially sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) have been studied by differential scanning calorimetry (DSC). For an SPPO of given degree of sulfonylation, a miscibility window in terms of the isomeric composition of the brominated copolymer was seen; the location and width of the window was a function of sulfonylation. In general, copolymers with a higher content of p BrSt exhibit miscibility with SPPOs with higher degrees of sulfonylation. Upon annealing to temperatures of 280° and 320°C, only small changes in the miscibility regime were observed. The miscibility behavior was analyzed on the basis of the mean‐field theory in terms of the individual segmental interaction parameters. © 1994 John Wiley & Sons, Inc.