Dielectric studies of the β1 and β2 processes of poly(alkyl methacrylate) polymers

Abstract

Dielectric studies have been made in the frequency and temperature ranges 10–10⁵ Hz and 80–240 K on poly(methyl methacrylate)(PMMA), poly(ethyl methacrylate)(PEMA), poly(n-butyl methacrylate)(PnBMA), poly(isobutyl methacrylate)(PiBMA) and poly(n-octadecyl methacrylate)(PnODMA). In addition, similar studies were made on a number of simple methyl esters to assist in the identification of the polymer relaxations. Enthalpies of activation values were obtained for PnBMA, PiBMA and PnODMA within the range found for methoxy-group relaxation in monomeric esters. For the polymers, the absorption in the 180–229 K region, which has been termed a β₁ process, is accounted for predominantly by the presence of moisture in these highly hygroscopic specimens, while a strong candidate for the additional absorption in the 110–170 K range is alkoxy-group relaxation.