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A relation between methyl-group tunneling and viscoelastic relaxation has been found in dynamic mechanical studies of the backbone methyl relaxation in polymethyl methacrylate (PMMA). The pronounced curvature found in the plot of lnν versus 1/T for the methyl relaxations at low temperatures and the observed large isotope effect for fully deuterated PMMA are in qualitative agreement with tunneling theory.
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Williams et al. (1975) studied this question.
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