Shear degradation of vinyl polymers in dilute solution by high‐speed stirring

The degradation of polyisobutylene and polystyrene resulting from high‐speed stirring of their dilute solutions has been investigated. Maximum degradation was obtained in “poor” solvents, at low temperatures and at highest possible rates of shear. The lower limit of the intrinsic viscosity reached for polyisobutylene in benzene solution was 1.30 as measured in cyclohexane at 30°. For polystyrene the lowest molecular weight attained is represented by an intrinsic, viscosity of ca. 0.75 in methyl ethyl ketone at 25°. The polymers were sheared in the presence of iodine and the amounts of iodine incorporated into the polymers measured radiochemically. The amounts of iodine incorporated during shear were of the same order of magnitude as the number of chain scissions calculated on the basis of the decrease in intrinsic viscosity.