Solubility and molecular size distribution of crosslinked polystyrene

Abstract Polystyrene, in common with a number of other long chain polymers, can be crosslinked by exposure to high energy radiation, the degree of crosslinking being directly proportional to the radiation dose. Measurements were made of the solublity in benzene and toluene, as a function of degree of crosslinking. A theoretical derivation is given for the sol fractions of a long chain polymer as a function of the crosslinking index γ, assuming that the initial molecular size follows a Poisson (random probability) distribution. The relationship between s and γ is shown to be: According to this formula a gel forms if γ> 0.5. An extension to deal with the possibility of chain fracture is described. A comparison of the observed solubility curve with this formula, and with that given by Flory for a uniform initial molecular size shows that only the former agrees with the experimental data. Little or no chain fracture occurs due to adiation.