Glass transition behavior and miscibility in blends of poly(vinyl p-phenol) with two homologous aliphatic polyesters

New miscible blend systems comprised of poly(4-vinyl phenol) (PVPh) and a homologous series of polyesters of different CH2/CO ratios (from 4.5 to 7) was discovered. Miscibility has been confirmed using differential scanning calorimetry, Fourier-transformed infrared spectroscopy, and scanning electron microscopy. The PVPh/polyesters blends investigated exhibited a single composition-dependent glass transition and homogeneous phase morphology, and they similarly exhibited a cusp in the Tg-composition relationships. This work further extended the range of aliphatic polyesters that are known to be miscible with PVPh. The Flory–Huggins interaction parameter (χ12) or energy density (B) obtained from analysis of melting point depression for PVPh/PEAz and PVPh/PHS blends are of negative values. More interestingly, the specific interactions in the PVPh/polyester blends change with the corresponding different structures in the polyester component. For the PVPh/PHS blend whose polyester constituent possesses a lower carbonyl density in the main chain (average CH2/CO ratio=7), the energy density B was found to be −1.17 cal cm−3. This value is significantly lower than those for either the PVPh/PEAz (CH2/CO=4.5) blend system (B=−7.72 cal cm−3). Miscibility, specific interactions, and peculiar Tg-composition relationships in the blends of PVPh with selected homologous polyesters are discussed.