Differential scanning calorimetry and one- and two-dimensional Fourier transform infrared (FTIR) spectroscopies have been used to investigate the miscibility of and specific interactions between poly(styrene-co-vinyl phenol) (PSOH) and poly(vinyl phenyl ketone) (PVPK) upon varying the vinyl phenol content of the PSOH copolymer. The FTIR spectra revealed that the phenol units of PVPh interact strongly with the C=O groups of PVPK through intermolecular hydrogen bonding, and more weakly with the aromatic rings of PVPK through intermolecular pi-pi interactions. A miscibility window exists when the vinyl phenol fraction in the copolymer is greater than 20 mol% in the PSOH/PVPK blend system, as predicted using the Painter-Coleman association model. (c) 2008 Elsevier Ltd. All rights reserved.