| Abstract: | The effects of γ-radiation on aqueous polystyrene emulsions were followed by measurements by intrinsic viscosities of soluble polymer in toluene. Estimates of incipient gel dose from intrinsic viscosity data do not coincide closely with those from measurements of gel content. This uncertainty and those in molecular weight averages make it difficult to assign a precise value to G(crosslink), even when the scission crosslinking ratio in the particular system is reliably known. The intrinsic viscosity of sol polymer in the postgel region decreases with increasing dose to an asymptotic value. The decrease is as expected if larger molecules are progressively linked into the gel network and the asymptote may be attributable to cyclization. Present theories of branching do not seem to be applicable for quantitative estimation of scission/crosslinking ratios caused by irradiation of polystyrene. This is probably connected with deficiencies in the theoretical connection between radius of gyration and intrinsic viscosity in good solvents. Diallyl fumarate and diallyl maleate increased crosslinking rates, but only at low doses. Chain scission was enhanced by addition of 1,2-dichloroethylene and 2,5-dimethylhexane-2,5-dihydroperoxide. |
