DYNAMICS OF MACROMOLECULAR CHAINS - ULTRASONIC STUDY OF POLYSTYRENE IN SOLUTION

Ultrasonic relaxation measurements on 2,4,6,8-tetraphenylnonane and a series of narrow molecular weight samples of polystyrene dissolved in ethyl benzene are reported as a function of temperature and frequency. These data are compared with previous ultrasonic studies on the configurational isomers of 2,4-diphenylpentane and 2,4,6-triphenylheptane which have shown that the relaxation frequency of the isotactic triads or meso diads is always much lower than that determined for the syndiotactic triads or racemic diads. The ultrasonic spectra are thus resolved to give two relaxation processes. The origin of the highest frequency relaxation, which needs up to ten monomer units, is thought to be an intramolecular process of the syndiotactic sequences. In this model, several segments of the polymer chain independently undergo the conformation change: gg tt gg tt gg ⇆ tt tt gg tt The absorption of energy in the low frequency range may be associated with a crankshaft motion. © 1979.