Dielectric relaxations in poly(di-n-alkyl itaconate)s

The dielectric spectra for the series poly(dimethyl itaconate) to poly(di-n-octyl itaconate) have been measured and are discussed within the context of a main-chain-side-chain nanomorphology. The major dielectric event is associated with the calorimetric glass transition. In contrast to methacrylate family of polymers, it is not possible to detect separate contributions to this relaxation from a localized ß-process and the cooperative backbone a-process. Different rotational barriers for each of the two side groups suggest that the ß-process will be a broadened superposition of two relaxations. The longer side-chain itaconates show a second-high-frequency process which is assigned to the alkyl side chains relaxing independently within their own domains. This feature is absent in the corresponding methacrylates but is observed here to the greater level of nanophase formation in the itaconates and the presence of the second ester unit in the itaconate repeat unit structure. The longer side-chain di-n-alkyl itaconates exhibit two calorimetric glass transitions, and it is suggested that both the lower temperature glass transition and the high-frequency dielectric dispersion originate in the same side-chain relaxations.