Enhancement of miscibility in blends of poly (vinyl methyl ether) and poly (α-methylstyrene)s modified by incorporation of hydrogen-bonding sites

Poly (a-methylstyrene) and poly (vinyl methyl ether) do not form one-phase blends when mixed together. This situation can be changed if the poly (a-methylstyrene) is modified by introducing hydrogen-bond donor groups into the phenyl ring. Two groups of differing donor strength, methylcarbinol and trifluoromethylcarbinol, were selected, and modified poly (a-methylstyrene) samples, with varying degrees of substitution of these groups, were prepared. If the amount of the modifying group incorporated exceeded 4 mol% then one-phase blends of these copolymers with poly (vinyl methyl ether) could be prepared. The effect of the number and strength of these hydrogen-bonding sites on the phase stability of the blends was measured by locating the lower critical phase separation temperature in each blend. The glass transitions of the blends were found to be normally higher than those predicted from a simple rule of mixtures and reflect the extent of hydrogen-bond formation in the blends. This behaviour could, in part, be described by the K wei equation. © 1992.