Longitudinal acoustic mode in polymers. IV. LAM-3 of the general perturbed rod and applications to paraffins and polymers

Abstract

The dependence of the LAM-3 frequency on the various parameters of a perturbed composite elastic rod has been calculated. Together with the previously calculated nonlinear variation of LAM-1 with these parameters, it can be expected that experimental measurements of both of these bands will permit a more detailed analysis of properties of long-chain molecules. The predictions of the theory are in complete agreement with experimental results on n -paraffins. For data on polyethylene and poly(ethylene oxide) reasonable solutions can be found, although the experimental information on polymers is not yet accurate enough or sufficiently devoid of assumptions to permit definitive conclusions to be reached.