THIN-FILM BEHAVIOR OF POLY(METHYL METHACRYLATES) .6. MONOLAYER PHASE-BEHAVIOR IN RELATION TO STEREOCOMPLEXATION IN MIXED MONOLAYERS OF I-PMMA AND S-PMMA

The stereocomplexation process in mixed monolayers of isotactic and syndiotactic poly(methyl methacrylate) is efficient only when low molecular weight samples are used. This phenomenon can be explained by an increasing tendency for phase separation in the monolayer upon using higher molecular weight samples, leading to larger domain sizes and a limited mutual accessibility: especially the use of high molecular weight syndiotactic PMMA appears to result in strong aggregation processes of these chains caused by the strong cohesive intersegment interactions at the air-water interface. This hypothesis is corroborated by the observation that addition of stereoblock PMMA strongly enhances the efficiency of the stereocomplexation process, thus acting as a compatibilizer, dispersing the s-PMMA chains in the monolayer.