| Abstract: | The majority of compatible polymer mixtures known so far has been rationalized by assuming special interactions between the different polymers or by specific repellent forces within certain types of copolymers. Thus, the compatibility of PMMA with special copolymers of styrene and acrylonitrile is explained by an intramolecular repulsion within the copolymer between the two comonomers styrene and acrylonitrile. In our opinion this phenomenon is not limited to copolymers, but also holds for explaining the compatibility of various homopolymers such as PVDF/PMMA. To this end we simply regard the homopolymer PVDF (-CH2-CF2-) as a copolymer of -CH2- and -CF2- “monomers”. By the same token it is possible to assume repellent forces within the PMMA monomer units (i.e. repulsion between the CH2-C(CH3) and the polar carbonyl group). Those strong repellent forces within the PVDF and PMMA homopolymers can be reduced by mixing the two species. This concept of repulsive forces within monomers as a driving force for polymer-polymer compatibility can be used to search for new classes of compatible polymers. This will be demonstrated with the polystyrene/polyalkylmethacrylate blends. Thus, with comparable geometry in the side chains, polystyrene and polymethacrylic esters will form compatible blends, as born out in the systems polystyrene/polycyclohexyl methacrylate or poly-tert-butyl styrene/poly-3,3,5-trimethylcyclohexylmethacrylate which are compatible in all proportions. Taking into account certain steric prerequisites, one can even obtain compatible blends lacking exothermic interaction. |
