RANDOM COPOLYMER BLENDS OF STYRENE, PARA-FLUORO STYRENE AND ORTHO-FLUORO STYRENE

This study completes the investigation of the phase behaviour of polymer blends involving styrene (S), ortho-fluoro styrene (oFS) and para-fluoro styrene (pFS). As before, due to the proximity of the glass transition temperatures of most blends investigated, the miscibility or immiscibility is established using the alternative thermal analysis method based on enthalpy recovery of samples annealed in the glassy state. In most respects the phase behaviour is similar to that of the corresponding chlorinated systems. The value of the Flory-Huggins parameter chi(S,oFS) is much smaller than chi(S,pFS). However, the latter is approximately the same as chi(oFS,pFS) and, as a consequence, a miscibility window as found in the system PS/P(oClS-co-pClS) is only present in PS/P(oFS-co-pFS) blends for rather low molecular weights.