Acoustic studies of solutions of narrow molecular weight polystyrene in toluene

Abstract

Acoustic relaxation measurements on a series of narrow molecular weight samples of polystyrene dissolved in toluene are reported. The low frequency (ca. 1 MHz) limiting values of the absorption coefficient show a molecular weight dependence below 10 000, decreasing with decreasing molecular weight. Similarly, the characteristic frequency for the observed relaxation is molecular weight dependent below 10 000, increasing with decreasing molecular weight.

This first unambiguous evidence of a molecular weight effect is interpreted in terms of normal mode, segmental mode and end group contributions. The results suggest that the principal contribution to the relaxation comes from the segmental process, and that the “end group” from the point of view of acoustic activity extends over several monomer units and experiences more ready conformational change.