縦波によるPMA-アセトン溶液の緩和現象

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As a molecular model of the longitudinal wave relaxation at MHz range for a polymer solution, Miyahara et al. proposed the crankshaft model with single thermal relaxation. Ludlow et al. reported the model with double motions in polymer chain, regarding it as a double relaxation. Recently, Ikeda et al. reported that the MHz range compressibility of PMA in acetone solution was abnormal and the compressibility of high molecular weight was higher than 1×10^6. It was suggensted that the phenomena were related with the molecular motion during the longitudinal wave relaxation at MHz range for the polymer solution. In this study, the molecular weight dependence of the molecular motion taking place during the longitudinal wave relaxation at MHz range in PMA-acetone solution was determined by the ultrasonic method. Two PMA samples with different molecular weights (B-3, 1×10^6 and -3, 56×10^4) were prepared. The excess absorption of PMA-acetone solution was estimated from the difference between the absorption of polymer solution and that of solvent. The result of C-3 solution was a single relaxation (hypothetical thermal relaxation). The result of B-3 solution was analyzed by the double relaxation theory. The relaxation frequencies obtained were 4 MHz and 40 MHz. The molecular model of relaxation for C-3 sample was given as the rotational isomer of a head-tail bond in polymer chain (ΔH゜=220 cal/mol, ΔH≠=1 600 cal/mol). The second relaxation at 40 MHz for B-3 sample was presumed to be correlated with the spreading of polymer chain, based on the solvent dependence of the relaxation.
社団法人日本材料学会の論文
1973-05-15

縦波によるPMA-アセトン溶液の緩和現象

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