メタアクリル酸エステル系列重合体の誘電的性質

Abstract

The frequency dependences of ε' and ε" at various fixed temperatures for polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), polybuthyl methacrylate (PBMA), polyisobuthyl methacrylate (PIBMA), polycyclohexyl methacrylate (PCMA) and polynonyl methacrylate (PNMA) were measured over wide frequency and temperature ranges.The α- and β-absorptions were observed in the cases of PMMA and PEMA, the α-, β- and γ-absorptions were observed in the case of PCMA, and the only one absorption was observed in each of PBMA, PIBMA and PNMA. The absorption in PBMA, PIBMA and PNMA are inferred to be the α-absorptions in which the small β-absorptions hide themselves.The magnitudes of the β-absorptions in PMMA and PEMA increase with increasing temperature, and the magnitude of PMMA with larger dipole concentration is larger than the latter. As for the α-absorptions, the temperature dependences of the magnitude cannot be discussed, since the magnitude of the α-absorption cannot be determined independently. However, the sums of the magnitudes of the two absorptions can be determined, which decrease with increasing temperature. Comparing these values at a fixed temperature, the polymer with the larger dipole concentration is found to have the larger value.The shapes of the α-absorption and the β-absorption become sharper with increasing temperature. The shape of the α-absorption in PNMA with the most loose molecular packing is the sharpest among the α-absorptions in these polymers. There are, however, not so remarkable differences between the shapes of the β-absorptions of PMMA and PEMA.When the mean values of the apparent activation energies for the α-absorptions are compared, PNMA with the most loose molecular packing shows the smallest value among the above polymers. In the case of the β-absorption, however, no great difference was observed among the apparent activation energies, so long as the side group is methyl- or ethyl- ester group.