Molecular weight distribution of polystyrene made by anionic polymerization

A set of polystyrenes of varying molecular weights was synthesized by anion ic polymerization under identical conditions, and their molecular weight di stributions were critically examined. Polymerization of styrene was initiat ed with 2-butyllithium in cyclohexane at 45 degrees C. During the polymeriz ation, seven aliquots of the reaction mixture were taken out at various rea ction times using a cannula and terminated. The polymerization time varying molecular weights and molecular weight distributions of the polystyrenes w ere analyzed by temperature gradient interaction chromatography (TGIC) as w ell as size exclusion chromatography. The molecular weight distribution of the polystyrene approaches the Poisson distribution in the late stages of t he polymerization, in accordance with the early prediction of Flory. We als o confirmed that the molecular weight distribution of polystyrenes determin ed by TGIC is close to the true value.