INFLUENCE OF HYDROGEN-BONDING ON THE FORMATION OF ONE-PHASE BLENDS IN BINARY-MIXTURES OF MODIFIED POLY(ALPHA-METHYL STYRENE) WITH ALKYL ACRYLATE, ALKYL METHACRYLATE AND DI-ALKYL ITACONATE POLYMERS

Two series of poly(alpha-methyl styrene), PalphaMS, based copolymers have been synthesized. In the PalphaMS (I) series the phenyl ring in the alpha-methyl styrene unit has been modified to varying degrees by the introduction of a methyl carbinol unit, whereas the trifluoro methyl carbinol unit has been used in the PalphaMS (II) series. These groups are potential hydrogen bond donor sites of differing acidic strength. It has been found that the introduction of these specific interaction sites allows the formation of one-phase blends with polymers containing an acceptor site, with which unmodified poly(alpha-methyl styrene) is immiscible. When these acceptor polymers are poly(alkyl acrylate)s and poly(alkyl methacrylate)s then one-phase blends are obtained with the methyl, ethyl and t-butyl derivatives. The range of one-phase blends can be extended to include the n-propyl derivatives if the modified PalphaMS are mixed with poly(di-alkyl itaconate)s. Glass transition temperatures, T(g), and lower cloud point (LCP) temperatures have been recorded for all the one-phase blends. The T(g) values are usually higher than predicted by the simple rule of mixtures and all blends then phase separate on raising the temperature well above T(g). These observations, and the differences in phase equilibrium behaviour exhibited amongst the various blends, are discussed in relation to steric restrictions to hydrogen bond formation, and the effect of both the number and strength of the hydrogen bonds formed on the phase stability of the blends.