SELECTIVE ACCUMULATION OF FUNCTIONAL-GROUPS AT THE FILM SURFACES OF STEREOREGULAR POLY(METHYL METHACRYLATE)S

Contact angles of water on stereoregular poly(methyl methacrylate)s (P MMA) solvent-cast in the form of films against a glass substrate were measured by using the sessile drop method. The syndiotactic films exhi bited contact angle values indicative of relative dominance of the non polar alpha-methyl and methylene groups of polymer chains at the air-s ide surface and the polar ester groups at the glass-side surface of th e films. The selectivity in the surface exposure of functional groups increased rapidly with syndiotacticity. On the contrary, the wetting r esults for the isotactic films showed no effect of the polarity of con tacting medium on the surface chemical composition and the wettability of the films represented an average for alpha-methyl, methylene, and eater groups both at the air-side and at the glass-side surface. The o bserved influence of tacticity on the surface activity of stereoregula r PMMAs was interpreted in terms of the surface conformational structu re of these materials.