高分子の緩和過程と温度との関係

抄録

The dielectric properties of five crystalline polymers and four amorphous polymers have been measured over the frequency range of 10^-1cps (or 10^-4cps for four polymers) to 10⁶cps and the wide temperature range. Two or three dielectric absorptions which have been designated as α, β and γ absorption with descending temperature have been observed for each polymer and all absorptions are due to the molecular motions in the amorphous region.
In the crystalline polymers, mechanisms of these absorptions have been discussed using results of the studies of the crystall growth processes. In vinylidene chloride copolymer, polychlorotri-fluoroethylene, polyoxymethylene and polyhexamethylene adipamide, the crystall growth has been detected by the density or X ray measurement in the temperature range where only the β absorption can be observed and the α absorption cannot be observed. Moreover the β absorption is related to the glass transition. Consequently it is concluded that the β absorptions of the four polymers are due to the motions of the main chains in the amorphous region. Supposing that the α absorptions of the four polymers are due to the motions of the main chains in strained amorphous region, the region has been searched by the dielectric measurements of polychlorotri-fluoroethylene samples having different degree of crystallinity. If two samples having different size of crystallites are compared at the same degree of crystallinity, the magnitude of the β absorption of the sample having larger crystallites is greater than that of the sample having smaller crystallites but the magnitude of the α absorption of the former is less than that of the latter. Moreover the positions of the α and the β absorption may be coincide with each other at the melting temperature. Consequently it is conjectured that the strained amorphous region is the surroundings which extend to a definite distance from crystallites and the amorphous region is the region between the strained amorphous regions.
In four amorphous polymers and a crystalline polymer, polyethylene terephthalate whose degree of crystallinity is nearly zero, the α absorption is related to the glass transition and may be due to the motions of the main chains. Generally the magnitudes of the β absorptions of these five polymers are considerably smaller than those of the four crystalline polymers mentioned above. The β absorption of an amorphous polymer, polymethyl methacrylate, is due to the motions of the side chains. It is uncertain whether the mechanisms of the β absorptions of the remaining four polymers and γ absorption of polyhexamethylene adipamide are the same as that of polymethyl methacrylate.
The temperature dependences of the dielectric relaxation times have been analized in terms of the apparent activation energy ΔH^*. For several absorption processes, ΔH^* increases with decreasing temperature and decreases after arrival at the maximum value. This anomalous phenomenon is related to dielectric transition that the magnitude of the absorption decreases sharply with decreasing temperature. The origin of the phenomenon is discussed. On the other hand, ΔH^* increases with decreasing temperature and not shows maximum for the absorption processes in which the dielectric transition is not observed.