| Abstract: | Solutions of polystyrene of molecular weight 4.5 × 106 and 8.4 × 106 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 CCl4 of the solvent, and polymer concentration C0. In the dilute region (C0 < 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 (C0 > C*) σ decreased significantly as C0 was increased. |
