Effects of applied pressure and polymer architecture on the second virial coefficient of polystyrene solutions

Second virial coefficients (A₂) of dilute polystyrene (PS) solutions in good, theta (θ) and poor solvents have been measured as a function of applied pressure using membrane osmometry and static light scattering. Membrane osmometry arid static light scattering equipment, designed to function at pressures in the range (0.1 ≦ P/MPa ≦ 6.0)and (0.1 ≦ P/MPa ≦ 35.0), respectively, have been used in these measurements, and the resulting pressure coefficients (dA₂/dP) are measures of the effect of pressure on solvent quality. For the system PS/toluene, membrane osmometry and SLS-obtained values ofdA2/dP are compared.The effect of polymer architecture on the second virial coefficient has also been studied with static light scattering measurements on linear(L)-star(S) polystyrene solutions at atmospheric pressure. Second virial cross coefficients between linear and star polystyrenes of similar molecular weight (A_2(l-s)) quantify the extent of linear-star PS interaction in good,θ , and poor solvents. Linear-star polystyrene interactions are preferred to polystyrene-solvent interactions in the good solvent (toluene). However, in θ (cyclohexane) and poor (MCH) solvents, there is no difference between linear-star and polystyrene-solvent interactions.