The degradation of polymer molecules in solution under the influence of ultrasonic waves. Part II. The rate equation and the limiting degree of polymerization

Abstract

AbstractThe breaking of polymer bonds in solutions of polystyrene, polyvinyl acetate, and polymethyl methacrylate in benzene and toluene while under the influence of ultrasonic irradiation has been studied by following the consumption of a radical scavenger, α,α′‐diphenyl‐β‐picryl hydrazyl added to the solution. The results are consistent with the rate equation proposed in an earlier paper, dBi/dt = k(Pi – Pe)ni and its relevant solutions, where dBi/dt, Pi and ni are, respectively, the rate of breakage of bonds, the degree of polymerization, and the number of molecules of the ith species, and where Pe is the limiting degree of polymerization, k is a constant, characteristic of the system and dependent on the weight concentration of the solution. Earlier literature is discussed and, in one case, the results are found to be more consistent with the above equation than with the forms: dB/dt = k(P ‐ Pe) and dB/dt = k log P/Pe. Values of Pe found by extrapolation are 1700, 2000 and 2800, respectively, for polystyrene, polyvinyl acetate, and polymethyl methacrylate. The various values of Pe for these systems to be found in the literature are discussed.