Ultrasonic relaxation studies of poly(methylphenylsiloxane) and its solutions in toluene

Abstract

Ultrasonic attenuation measurements, covering the frequency range 5–100 MHz and the temperature range 253–298 K, made on two samples of poly(methylphenylsiloxane) of nominal molecular weight 4 × 10³(MS 550) and 4.6 × 10⁵(MS 350) and on their solutions in toluene are reported. The acoustic attenuation has been compared with the amplitude predicted for a viscoelastic relaxation process. In the case of the MS 550 polymer a good correspondence between experiment and Navier–Stokes theory was observed. In contrast, the MS 350 polymer exhibited a poor correspondence between experiment and theory. This is found to arise from the presence of a significant amount of unreacted cyclic material which exhibits a conformational relaxation.