Conformations of Ring Polystyrenes in Semidilute Solutions and in Linear Polymer Matrices Studied by SANS

Abstract

Conformations of highly purified ring polystyrene, R-70, with the molar mass of 70 kg/mol, in a good solvent and in linear polymer homologue matrices were examined by small-angle neutron scattering (SANS) measurements. The radii of gyration Rg of R-70 were estimated by the Guinier’s approximation from the SANS profiles obtained, and the polymer volume fraction Φ dependence of Rg2 was discussed. In deuterated toluene as a good solvent, R-70 exhibits the Rg2 ∼ Φ–0.29±0.01 dependence at high Φ above the overlap volume fraction, Φ0* (i.e., 1 < Φ/Φ0* < 20). This exponent −0.29 shows stronger Φ dependence than that for semidilute solutions of linear polymers, −0.25, predicted from the scaling theory, suggesting that the ring expands more sensitively than linear chains when Φ decreases in semidilute regime. In contrast, the Φ dependence of Rg2 of R-70 is evidently weaker than that of the recent simulation for ring polymer solutions (Rg2 ∼ Φ−0.59) by Reigh et al. This difference is thought to originate from the d...