Organic Solvent Nanofiltration with a Poly(dimethylsiloxane) Membrane: Parameters Affecting its Sieving Properties

In this study, retention experiments were performed to characterize the variable sieving properties of a poly(dimethylsiloxane) (PDMS) membrane in relation with operating parameters. The swelling, transmembrane pressure, and temperature are all known to impact the physicochemical properties and morphology of PDMS polymer and were therefore varied for the purposes of our retention experiments which assessed them with the homologous series of polyethylene glycols (PEGs; 200-1500 g mol(-1)). The objectives were twofold-first, to evaluate the capacity to induce a targeted molecular weight cutoff (MWCO) by selecting appropriate filtration conditions and second to better understand the mechanisms involved during solvent-resistant nanofiltration with PDMS. The selected solvents or solvent/solvent mixtures used throughout this study were found to induce swelling ratios of 1.16 (ethanol/ethyl acetate: 25/75), 1.26 (ethyl acetate), 1.33 (ethyl acetate/toluene: 50/50), and 1.41 (toluene), respectively. Linear correlations were obtained between the MWCO and the swelling ratio induced by each solvent and between the MWCO and the transmembrane pressure. Pore size calculations using solvent flux and retention data confirmed the variable sieving properties of the PDMS membrane in relation to the solvent-induced swelling and applied transmembrane pressure. In addition, the study of the solute-transfer rate through several operating conditions showed that both diffusive and convective transports occurred for the PEG solutes and that their respective contributions appeared dependent on the variable pore size of the PDMS membrane. (C) 2014 Wiley Periodicals, Inc.