Effects of solvent goodness and polymer concentration on rejection of polystyrene from small pores

Solutions of polystyrene of molecular weight 4.5 × 10 6 and 8.4 × 10 6 in mixed solvents of carbon tetrachloride/methanol were filtered through track‐etched mica membranes at low membrane velocities. The unperturbed hydrodynamic radius of the polymer was always larger than the pore radius. The reflection coefficient σ, defined as the fraction of polymer held back by the membrane, was determined from material balances as a function of solvent flow rate per pore q , volume percent CCl 4 of the solvent, and polymer concentration C 0 . In the dilute region ( C 0 < C * ) σ was found to depend primarily on q and was essentially independent of chain size (or solvent goodness), molecular weight, and pore radius. In the semidilute region ( C 0 > C * ) σ decreased significantly as C 0 was increased.