Light scattering study of intrachain conformational relaxation of hyperbranched polystyrene chains in a marginal solvent

Abstract

So far, much less attention has been paid to the dynamic behavior of branched polymers under marginal solvent condition. This work reports the first study of the intrachain conformational relaxation of hyperbranched polystyrene (PS) chains under the marginal solvent condition in the dilute regime. Specifically, the solvents of ethyl acetate (EA) and toluene (Tol) are selected for comparison. By a combination of static and dynamic light scattering measurements, a few findings have been revealed: 1) the weight average of molar masses (Mw) of hyperbranched PS chains are determined to be 7.33 × 107 and 8.02 × 107 g/mol in Tol and EA, respectively, implying the single chain state under both solvent conditions; 2）the value of reduced first cumulant (Γ*) at very high q-regime, i.e., Γ*(∞), is determined to be around 0.026 ± 0.002 in EA, which is not only smaller than the smallest Γ*(∞) ≈ 0.052 ± 0.002 reported for linear chains in literature under theta and good solvent conditions, but also much smaller than the reported Γ*(∞) ≈ 0.033 ± 0.003 for hyperbranched chains in literature under good solvent condition, and the result implies the reduced hydrodynamic interactions. Although the excluded volume effect is relatively weak in the marginal solvent, the present study supports that the existence of weak binary interactions between segments still influence the conformational behavior significantly.