Abstract
Ultrasonic attenuation at 10MHz is measured for three poly(methacrylate esters) and polypropylene, and the attenuation peak due to motion of the α-methyl group is observed for each polymer. Dynamic mechanical relaxations, NMR line narrowing and T1 minima due to methyl group motion are classified into four types according to the location of methyl group in the molecule. The dispersion map is analysed according to the theory by Das. The relaxation time of mechanical relaxation is found to obey the classical theory which does not include the quantum-mechanical tunnelling effect. Mechanical relaxation is interpreted in terms of energy exchange between the methyl group and the backbone chain. Relaxation strength is proportional to absolute temperature. The results of a theoretical treatment of relaxation strength agree satisfactorily with those obtained by experiment.
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Tanabe, Y., Hirose, J., Okano, K. et al. Methyl Group Relaxations in the Glassy Phase of Polymers. Polym J 1, 107–115 (1970). https://doi.org/10.1295/polymj.1.107
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DOI: https://doi.org/10.1295/polymj.1.107