Conformations of Ring Polystyrenes in Bulk Studied by SANS

Abstract

We prepared five pairs of hydrogenous and deuterated ring polystyrene samples over a wide range of molecular weights (10 kg/mol ≤ Mw ≤ 400 kg/mol) and investigated their chain conformations in bulk by small-angle neutron scattering (SANS) measurements. From the SANS profiles obtained, we estimated the radii of gyration Rg of the ring polymers by the Guinier approximation. Rg can be related to the degree of polymerization N as Rg ∼ N0.47. This scaling exponent ν = 0.47 ± 0.01 is evidently smaller than that for the Gaussian chains (ν = 0.50) but higher than previous experimental reports (ν = 0.42–0.43). Then our data were compared with various simulation and experimental data by introducing the entanglement degree of polymerization Ne for linear polymers as a normalized parameter. Rg of three smaller rings, i.e., R-10, R-30, and R-70, where the numbers denote molecular weights in kg/mol unit, are in good agreement with simulation results, while two larger rings, R-100 and R-400, exhibit higher Rg values tha...