The Influence of Crystallization Conditions on Radiation Effects in Polyethylene - II. Crystallization from Concentrated Solutions

It was shown in the preceding paper 1 that polyethylenes crystallized from the melt and from dilute solution were affected differently by electron irradiation, the former becoming insoluble at much lower doses than the latter. In addition to their inherent interest for radiation studies, these findings should also be of value for morphological investigations, as the morphological state of the specimen may be reflected in the effect of the radiation on solubility. As was concluded in the preceding paper, 1409 1410 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1961 the different behavior of the bulk and dilute solution crystallized specimens indicates different morphologies. In particular, the higher solubility of the irradiated solution crystallized specimens is readily explicable in terms of intramolecular crosslinks forming within the folded chains of such single-crystal preparations. Accordingly, the lower proportion or even absence of such intramolecular linkages in the bulk would indicate that the molecules are not folded in such specimens. This appears to support the view that we are dealing with two distinct states of matter in the two kinds of specimens, a point which is nowadays widely debated. 2 ' 3 According to recent theoretical work by Lauritzen and Hoffman, 4 crystallization from dilute solution should occur via chain folding and that from the melt through the traditional bundle-like aggregation, a transition occurring between the two as the concentration of the solution is increased.