Melt Rheology of Tadpole-Shaped Polystyrenes

Abstract

A series of highly purified tadpole-shaped polystyrene (PS) samples were prepared by anionic polymerizations and multistep HPLC fractionations, and their linear melt rheology was investigated. Three tadpole samples were composed of a common ring chain (R-60; Mw = 59.8 kg/mol) and three different lengths of linear chains (L-30, L-70, and L-120; Mw = 27.1, 68.9, and 122 kg/mol, respectively), all of which were longer than the entanglement molecular weight (Me = 18.0 kg/mol for PS). All tadpole samples revealed remarkably slower terminal relaxation than the constituent ring or linear chains and also than the ring/linear blends. These results are evidently owing to the newly generated characteristic entanglements such as the intermolecular ring–linear penetrations. Two rheological parameters, i.e., the zero-shear viscosity, η0, and the steady-state recoverable compliance, Je, were estimated, and their molecular weight dependence was discussed. Tadpoles used in this study exhibited a drastic viscosity enhancem...