Influence of gamma irradiation on the molecular weight distribution and related properties of a polymer: Study through simulation and experiment

The morphology of a polymer system gets modified by gamma irradiation through scission and cross-linking of chains, which may occur simultaneously. The effect of gamma irradiation on the associated properties of poly(ethylene oxide), e.g. molecular weight distribution, viscosity and microstructure, is reported in the present paper. A computer simulation study is performed to model and understand the experimentally observed changes that are induced by gamma irradiation on the associated properties of the polymer. The primary assumption of the model considers terminal monomers of the chain to be inactive. The probability of a monomer to be a reactive site participating in scission or cross-linking is assumed to be proportional to its distance from the ends, and hence is maximum at the center of the chain. Correlation is established between the irradiation dose and simulation time steps using molecular weight distribution pattern and intrinsic viscosity. The dependence of polymer viscosity on the preparation techniques, e.g. ultrasonic and magnetic stirring, is studied and fitted with Huggins equation in lower concentration range. Solution parameters, like intrinsic viscosity and the Huggins constant, are determined from plot extrapolation and they are studied for their variation with irradiation dose and concentration. The change in polymer microstructures with irradiation dose is also reported.