Compatibility between polystyrene copolymers and polymers in solution via hydrogen bonding

It has been applied the concept of improving miscibility, by introducing and optimizing the extent of intermolecular hydrogen-bonding interactions between two polymers. We select a commodity polymer such as polystyrene, to study the compatibility in chloroform with poly(vinyl pyridine) and poly(vinyl pyrrolidone), both considered as proton acceptors. In order to enhance polymer–polymer miscibility, polystyrene is slightly modified by copolymerization with methacrylic acid, in the first case, and with vinyl-phenol comonomer, in the second one. In this way, two series of polystyrene-based copolymers are synthesized and characterized bearing ca. 8% (w/w) of –OH groups. The miscibility gaps through the binodal ternary phase diagrams, interpolymer interaction parameter from viscometry and the evaluation of the interassociation equilibrium constant, K, by FT-IR spectroscopy serve to analyze the effect of the spacing of interacting moieties along the polystyrene chain. Our results prove that polymer–polymer miscibility increases with an increase in the methacrylic-acid content in the copolymer chain; however, when the polar group is vinyl phenol, this continuous trend is disrupted.