QM TUNNELING AS A VISCOELASTIC RELAXATION MECHANISM

It is proposed that quantum-mechanical tunneling may be the viscoelastic relaxation mechanism for methyl group containing polymers at low temperatures. This proposal is based on the agreement of the tanδ peaks at given frequencies with the tunneling frequencies for methyl groups of reasonable barrier heights at corresponding temperatures. The proposed mechanism, in conjunction with published frequency-barrierheight correlations, allows the estimation of the barrier heights for a wide range of methyl groups from the knowledge of a single tanδ maximum. The barriers are in general agreement with those obtained by NMR techniques for similar materials.