Second and third virial coefficients of low-molecular-weight polyisoprene in 1,4-dioxane

Abstract

Light-scattering measurements were carried out on polyisoprene (PI) samples with weight-averaged molecular weights (Mws) ranging from 1.1×103 to 2.7×104 in 1,4-dioxane at and near the theta point, 35.3 °C, which is defined as the temperature at which the second virial coefficient A2 for sufficiently high Mw (larger than 1×104) vanishes. It was found that A2 at the theta point decreases with decreasing Mw for Mw1104. This was explained by the effects of both the three-segment interaction and the side-chain end. The binary-cluster integral for the side-chain-end segment and the PI segment was negative, revealing the attractive interactions between them. The third virial coefficient increased with decreasing Mw. This was also attributed to the side-chain-end effect.