Melt rheology of tadpole-shaped polystyrenes with different ring sizes

Abstract

In this study, linear melt rheology of a single-tail tadpole-shaped polystyrene, ST-30/80, having ring and linear sizes of M_R ∼ 30 kg mol⁻¹ and M_L ∼ 80 kg mol⁻¹, respectively, was examined, and the effect of the ring size on rheological properties of tadpole polymers was discussed by comparing with the data of the previously reported tadpole samples having M_R ∼ 60 kg mol⁻¹. ST-30/80 exhibits an entanglement plateau and shows a clearly slower terminal relaxation than that of its component ring and linear polymers. When the zero-shear viscosity η₀ for ST-30/80 is plotted against the molecular weight of a linear tail chain, the data point lies on the single curve of η₀ for 4- and 6-arm star polymers and the single-tail tadpoles with M_R ∼ 60 kg mol⁻¹. These results suggest that the tadpole molecule in this study spontaneously forms a characteristic entanglement network, i.e., the intermolecular ring–linear threading, in the same manner as the previous tadpole samples, even though the size of the ring part is just slightly larger than the entanglement molecular weight (i.e., M_R ∼ 1.8M_e).