1967 Volume 40 Issue 9 Pages 2063-2068
Ultrasonic investigations of aqueous solutions of polyethylene glycol solutions have been made by means of an ultrasonic pulse technique. Two samples of the polymer have been used, the molecular weights being 4000 and about 6000. The measurements of the sound velocity and of the absorption have been made on 5–30 wt% solutions of the polymers, together with an ethylene glycol-water mixture for the sake of comparison, over the frequency range of 5–45 Mc/sec. The temperature has been varied over the range of 10–70°C. It has been found that the velocity vs. temperature curve for each solution has a peak, and that the peak has a trend to shift to a lower temperature with the increase in the concentration. From the absorption data obtained, it has been found that a characteristic relaxation frequency appears near 40 Mc/sec at room temperatures. The magnitude of the absorption has been found to increase linearly approximately with the increase in the concentration, and to be independent of the molecular weight of the polymers at least in the range studied. From the temperature dependence of the relaxation frequency, the apparent activation energy of the relaxation process has been estimated to be not larger than 1 kcal/mol. It has been concluded from the results that the source of the relaxation process is not the hydrogen bonding between polymer molecules and water, as recently stated by G. G. Hammes et al. (J. Phys. Chem., 70, 1610 (1966)), but some intramolecular process.
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