α−β Splitting Region in the Dielectric Relaxation Spectrum of PEA-PEMA Sequential IPNs

The dielectric relaxation spectra of poly(ethyl acrylate)-i-poly(ethyl methacrylate) sequential interpenetrating polymer networks, IPNs, are presented. In addition, dynamic-mechanical data were used to study the compatibility of the networks as the main relaxation predominates on the secondary relaxation in mechanical spectroscopy. When the IPNs are highly cross-linked, both networks are forced to mix at the molecular level, and as a consequence, a single main dynamic mechanical relaxation appears. By contrast, when the cross-linking density is small, the individual relaxation behavior of the component networks can be observed. The poly(ethyl methacrylate) networks with low cross-linking density show the merging of the secondary β dielectric relaxation and the main α relaxation with the same characteristics as the poly(ethyl methacrylate) chain polymer. This behavior changes, however, in the highly cross-linked network in which the influence of the main relaxation on the overall behavior is smaller, and it was not possible to separate the α and β components in the merging region. The incorporation of the poly(ethyl acrylate) chains to the cooperative motions of the poly(ethyl methacrylate) network shifts the α and β relaxations to a different extent, which induces changes in the shape of the spectrum in the merging zone.