SURFACE ENRICHMENT IN PS PVME BLENDS .2. THE EFFECT OF SPECIFIC INTERACTIONS IN THE BULK MIXTURE

The surface composition of blends of styrene copolymers, containing a hydrogen-bonding comonomer, with poly(vinyl methyl ether) has been estimated using infra-red reflectance spectroscopy. Surface enrichment by the polyether, which has the lower surface energy, is markedly less than that observed previously for poly(vinyl methyl ether)/polystyrene homopolymer blends. The extent of this effect depends on the strength of the hydrogen bond involved, and this in turn can be correlated with the degree of blend miscibility as determined by lower critical phase separation temperatures and heats of mixing. The findings confirm that surface enrichment depends not simply on surface energy differences but also on bulk mixing thermodynamics.