Interdiffusion of polydisperse Mw distributions subsequent to proton irradiation of PS melts

Abstract

Under exposure to ionizing radiation the molecular weights of polymeric matter changes via formation of crosslinks and scissions of chains. As a result the molecular weight ( M w) distribution of a polymer depends on the applied ion fluence and differs from the initial one, which in our case is of the Schulz–Zimm type. Statistical theories can be used to estimate the M w distribution. We study M w distributions in proton irradiated polystyrene (PS) thin films by diffusion measurements. As chains of different degrees of polymerization diffuse unequally fast diffusion depth profiles contain information about the involved M w distribution. Both irradiation and analysis with nuclear reaction analysis (NRA) were made at the Freiburg van de Graaff accelerator. As comparison gel permeation chromatography (GPC) measurements were conducted. However, the use of GPC is limited by the minimal amount of material needed and also does not work for very short chains in our case. Here we concentrate on the M w distributions, the measurements and the fitting procedure will be presented elsewhere.