The dielectric β-dispersions in the amorphous parts of the linear high polymers may be roughly classified into two categories according to their mechanisms.The first is of the dielectric β-dispersions in the high polymers whose dipoles are short and rigidly attached to their main chains such as polyvinylchloride (PVC), while the second is in the high polymers whose dipoles are long and flexible such as polymethylmethacrylate (PMMA).
In the preceding paper, the dielectric β-dispersions of these first group polymers are investigated from a standpoint that these β-dispersions would be attributed to the constrained small deformations of the main chains in the vicinity of their quenched positions in the high elastic medium. In this paper, both α- and β-dispersions of these second group polymers, especially of polymethylmethylmethacrylate, polymethylacrylate, and polyvinylacetate, are discussed making use of the site model. The behavior of the static dielectric constant near the glass transition temperatures, Tg, is also investigated with the aid of the site model.
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