The miscibility in blends of poly(cyclohexyl methacrylate) (PCHMA) with poly(4-vinyl phenol) (PVPh) and with copolymers containing vinyl phenol and styrene units (PSVPh) has been examined by Fourier transform infrared spectroscopy. The phase behaviour of the PCHMA/PSVPh system was predicted by means of association model of Painter and Coleman (PCAM) with a single interassociaton equilibrium constant (K-A) as well as by means of a new double interassociation model (D.I.M). The second interassociation equilibrium includes the weaker interaction between carbonyl and phenyl groups of CHMA and styrene (S) repeat units, respectively. In order to quantify the effect of free volume on miscibility, different contributions to free energy of mixing have been calculated. The predicted miscibility map did not change appreciably when compressibility effects were considered. On the other hand, by taking into account the second weaker interaction, better agreement between experimental and predicted miscibility maps is found for binary PCHMA/PSVPh blends. Finally, the D.I.M. has been extended to the case of ternary PCHMA/PS/PVPh blends. (c) 2005 Elsevier Ltd. All rights reserved.