Interaction of Polymers and Mechanical Waves

The "equilibrium" mechanics of polymers, the giant molecules of plastics and rubbers, have been quite elegantly developed in the range of high strains ("kinetic theory" of elasticity--Meyer, 1 et al). However, the molecular displacements as these strains, and, indeed, much smaller ones, occur, are little understood. Nevertheless, it is essential to know about detailed motions in connecting chemical structure with physical properties. Only in this way can there be obtained from the chemical industry compositions which will serve properly in telephone apparatus. 306 INTERACTION OF POLYMERS AND MECHANIC. 'AL W A V E S 307 Other studies have treated one way of getting at these mechanisms by relating stress relaxation, creep, viscosity, etc. to a distribution of molecular relaxation times (and energy barriers), as originated by K u h n . 3 , 4 Another approach is to strain polymers with periodic waves over a very wide spectrum of wavelengths, eventually going to frequencies comparable with those of the thermal vibrations of significant groups or segments in the macromolecules. The resulting dispersion or resonance phenomena can then be examined. Iience a mechanical radiation field can interact with the masses of elementary structural units, as the usual electromagnetic field interacts with atomic and group charges. In general, direct interpretations of this kind must be done with shear waves, and, at least, not only with longitudinal or ultrasonic waves. This kind of study is now proceeding using waves generated and followed by piezoelectric crystals connected in as actual electromechanical circuit elements (A.