Abstract
The time dependence of an absorption current in isotactic poly(methyl methacrylate) (PMMA) was measured from 10 to 600 s after the application of a step voltage at temperatures ranging from −54.0 to −95.5°C in order to determine the dielectric relaxation spectrum for the β-process separated from that for the α-process. The data on the absorption current in the glassy state thus obtained were converted to those on the frequency dependence of loss permittivity using the Hamon approximation. The results were reduced to a master curve by the method of reduced variables. The shape of the β-relaxation spectrum determined from the master curve is the same as that for atactic PMMA in the glassy state, but both activation energy and relaxation strength are about 1/2.5 times as large as those for atactic PMMA. The activation energy obtained from the temperature dependence of the shift factor is ca. 8 kcal mol−1. The value of the activation energy and the shape of relaxation spectrum thus obtained for the dielectric β-relaxation are found to be the same as those for the mechanical β-relaxation obtained from creep compliances of isotactic PMMA in the glassy state.
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Tetsutani, T., Kakizaki, M. & Hideshima, T. Relaxation Spectroscopy of the Dielectric β-Relaxation in Poly(n-alkyl methacrylate)s by Absorption-Current Measurements. II. Dielectric Relaxation Spectrum for Isotactic Poly(methyl methacrylate). Polym J 14, 471–476 (1982). https://doi.org/10.1295/polymj.14.471
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DOI: https://doi.org/10.1295/polymj.14.471
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