A New Model for the Evolution of the Molecular Weight Distribution of Polymers During Ultrasonic Chain Scission

Abstract

A new model for ultrasonic scission of polymer chains has been developed. The model takes the coiled nature of the polymer chains into consideration. The time evolution of the molecular weight distribution for several values of the solvent quality parameter is obtained using the new model. It is seen that the model leads to higher scission rates and lower final molecular weights for better solvents in accord with the experiments. Simulated gel permeation chromatography results are also in line with the experiments.

Kinetics of Ultrasonic Polymer Degradation: Comparison of Theoretical Models with On‐Line Data

“…Models for describing the molecular weight evolution during sonication include those of Schmid, [21,22] Baramboim, [23] Ovenall et al, [24] Rodriguez and Winding, [25] El'tsefon and Berlin, [26] Harrington and Zimm, [27] Glynn and Van der Hoff, [13,14] Doulah, [15] Malhotra, [28] Madras and Chattopadhyay, [29] Giz et al, [30] Tang and Liu [31] in historical order. Some of these models start from a scission mechanism and derive the molecular weight evolution from the proposed mechanism, while phenomenological ones describe the evolution of the molecular weight without proposing a scission mechanism.…”

“…Heterogeneous processes with a continuum of timescales, like dielectric relaxation and donor-acceptor energy transfer in fluorescence are commonly approximated by the stretched exponential function introduced by Kohlrausch in 1849. [43][44][45] The authors suggested that the average molecular weight evolution could be approximated as [30] …”

Depolymerization using sonochemical reactors: A critical review

“…Numerous theoretical [77,78] and phenomenological models [79][80][81] for ultrasonic polymer degradation have been developed to evaluate the kinetics of the ultrasonic degradation process based on the reduction in the average molecular weight during the process [82]. Various models describing the molecular weight evolution during sonication have been presented in the work of Ovenall et al [78], Harrington and Zimm [83], Glynn and Van der Hoff [84,85], Doulah [86], Malhotra [87], Madras and Chattopadhyay [25], Giz et al [80] and Tang and Liu [88].…”

“…Various models describing the molecular weight evolution during sonication have been presented in the work of Ovenall et al [78], Harrington and Zimm [83], Glynn and Van der Hoff [84,85], Doulah [86], Malhotra [87], Madras and Chattopadhyay [25], Giz et al [80] and Tang and Liu [88]. Some of these models start from a mechanism of scission and obtain the molecular weight evolution, while some describe the development of the molecular weight without proposing a scission mechanism.…”

“…A simplified statistical model (Eq. (10)) proposed by Giz et al [80], consider that longer polymers are stressed more and therefore broken down more easily as compared to shorter ones, and as a result the scission process has a range of time constants. Based on this assumption, they obtained the evolution of molecular weight distribution.…”