Broad-Band Dielectric Study on Poly(4-vinylphenol)/Poly(ethyl methacrylate) Blends

The dielectric relaxation behavior of miscible poly(4-vinylphenol)/poly(ethyl methacrylate) (PVPh/PEMA) blends has been studied using broad-band dielectric spectroscopy in the frequency domain from 10 -2 to 10 7 Hz and at temperatures between 30 and 180 °C. The α and β processes are resolved from the dielectric spectra by modeling with Havriliak−Negami (HN) functions. PVPh enhances the splitting between the α and β processes and provides a better understanding of the splitting and merging mechanism. Arrhenius plots support the proposal that the α and β processes have the same molecular origin above the merging temperature. The local β process in the blends originates from side-chain rotation of PEMA and is only slightly influenced by PVPh. On the other hand, the α process includes contributions from both components, and its relaxation time increases rapidly with PVPh concentration. However, a fragility plot reveals that the presence of PVPh does not change the cooperativity beyond shifting T g for the blends, which is inconsistent with the energy landscape model. The relaxation time for the merged αβ process also increases significantly as a result of the participation of PVPh. Because of the strong hydrogen bonding between PEMA and PVPh, the blends exhibit only slight dielectric broadening or concentration fluctuations.