Newly developed form factors for small-angle scattering have enabled measurements of cyclic polymers under non-theta conditions, when the rings become swollen due to favorable interactions with the solvent. Here, small-angle neutron scattering (SANS) measurements are made on cyclic polystyrene chains (Mn = 10 kg/mol, 15 kg/mol) and their exact linear analogs in cyclohexane as a function of temperature. SANS measurements, fit using the random phase approximation (RPA), indicate that cyclic polymers are more swollen than their linear counterparts, with a radius of gyration that scales as Rg ~ N0.53 near the θ-temperature, versus Rg ~ N0.50 for the linear chains. As temperature increases, linear polystyrene swells at a greater rate than the cyclic polystyrene, but with an exponent that is always less than the cyclic polymer. These results are interpreted using PRISM calculations and molecular dynamics simulations, which are in good qualitative agreement with the neutron scattering results.

Theory, simulation, and neutron scattering from cyclic polystyrene and exact linear analogs

255th National Meeting (2018)

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