Long-chain dynamics in binary blends of monodisperse linear polymers

Abstract

The linear viscoelastic properties of binary blends of monodisperse linear polymers of various polymers, including polyisoprene, polybutadiene, and polystyrene, are compared with the predictions of the model of Park and Larson (2004), which is an extension of the Milner-McLeish model [Milner and McLeish (1998)]. For each polymer system the model parameters needed in the predictions of the binary blend are obtained from experimental data for monodisperse polymers. For well entangled blends of nearly monodisperse polymers, the model predictions are in good agreement with experimental data for a wide range of values of the Graessley parameter Gr, which is proportional to the ratio of the reptation time of the long chain in the undilated tube to the constraint-release Rouse time. Our results show that for polymers of multiple chemical types, the terminal behavior of the long chain is controlled by reptation in an undilated tube for small Gr<Grc, and by reptation in a dilated tube for Gr>Grc, where Grc is around 0.06. For values of Gr near Grc, behavior intermediate between reptation in a dilated and an undilated tube is found.