HYDROPHOBIC ACCELERATION OF P-STYRENE-SULFONATE POLYMERIZATION BY GAMMA-CYCLODEXTRIN

Radiation-induced radical polymerization of p-styrenesulfonate (SS) in aqueous solution is accelerated in the presence Of 7-cyclodextrin (ga mma-CD). The polymer yield tends to be independent Of gamma-CD concent ration above [gamma-CD]/[SS] = 0.5, indicating that gamma-CD forms a 1 :2 complex with SS to promote the polymerization. p-Ethylbenzenesulfon ate (EBS) suppresses the accelerating effect of gamma-CD. This is attr ibuted to competitive complexation of EBS with gamma-CD. Molecular wei ght of the polymer becomes higher in the presence of gamma-CD. Molecul ar weight distribution curves of the polymers obtained at [gamma-CD]/[ SS] = 0.1 5-0.30 are clearly bimodal, suggesting contributions of comp lexed and dissociated propagating radicals. An aggregation of the 1:2 complexes is proposed to account for the independent propagation of th e complexed and dissociated radicals. Glucose (Glc), a component unit of CDs, also accelerates the polymerization, but to a smaller extent t han gamma-CD. The polymer yield continues to increase with Glc concent ration up to [Glc]/[SS] = 6, and is hardly affected by EBS. A hydropho bic aggregation of SS may be responsible for the acceleration of the p olymerization in the presence of Glc.