Self-association and interassociation equilibrium constants determined from i.r. studies of miscible poly(2,6-dimethyl-4-vinyl phenol) (PDMVPh) and poly(2,6-diisopropyl-4-vinyl phenol) (PDIPVPh) blends with poly(n-butyl methacrylate) and an ethylene-co-vinyl acetate (EVA) copolymer are used to calculate theoretical miscibility windows for the homologous series of poly(n-alkyl methacrylate)s and the entire copolymer composition range of EVA copolymers. Miscibility gaps are predicted to increase significantly for analogous blend systems in the series PDIPVPh > PDMVPh > poly(4-vinyl phenol). One factor contributing to this trend is the steric hindrance of the 2,6-dialkyl substituents, which serve to reduce the relative strength of self-association versus interassociation. Experimental i.r. studies of these blend systems corroborate the overall shape and size of the single phase region of the predicted miscibility windows.