By use of a pulse method, the sound absorption and sound velocity was measured in solutions of different concentrations of polystyrene in CCl4 and C6H6. The range of temperature extended from +3 °C to +60 °C and the frequency was continuously variable from 0,7 Mc/s to 333 Mc/s. The increase of absorption due to the vibrational relaxation of the pure solvent is in all solutions superimposed by another part of absorption, which can be explained (contrary to the interpretation given by R. Cerf, R. Zana, and J. Candau [see C. R. Acad. Sci. Paris 252, 681 (1961);252, 2229 (1961);254, 1061 (1962)]) by the model of a single relaxation process. The relaxation strength of that process is proportional to the concentration of the solution and decreases with increasing temperature. This can be explained by the assumption of a Schottky- anomaly in the molar heat capacity, caused by the energy difference of two rotational isomer configurations of the polystyrene chain. By neglecting the changes in volume and entropy of the rearrangement reaction, the experimental results yield an energy difference between the rotational isomers of 0,8 kcal/mol and an activation energy of 7,5 kcal/mol. © 1969 Dr. Dietrich Steinkopff Verlag.
