Using co-solvents and high throughput to maximize protein resistance for poly(ethylene glycol)-grafted poly(ether sulfone) UF membranes

Abstract

The surface of poly(ether sulfone) (PES) membranes were modified to reduce protein fouling by grafting poly(ethylene glycol) methyl ether methacrylate (PEG) onto the membrane. Photo-induced graft polymerization (PGP) was used with a recently developed high throughput platform (HTP). To optimize and improve PEG protein resistance, four different co-solvent additives (dimethyl chloride (DCM), dimethylene formamide (DMF), dimethylene sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP)) were mixed with aqueous PEG solution in order to examine co-solvent effects on grafting and filtration performance of PES- g-PEG surfaces. Bovine serum albumin (BSA, 1 mg mL −1) was used as model “foulant” protein and DI water and PBS filtration resistance and protein sieving were measured. The intensity of fouling was quantified by a fouling index ( R) and correlated with the degree of grafting (DG) using FTIR-ATR spectra. Lower R values were observed for grafting PEG in the presence of co-solvents than in their absence. The lowest fouling index ( R = 0.03 ± 0.04) was with a 0.2 mol L −1 PEG and 0.15 mol L −1 DCM mixture, where the DG was 0.05 ± 0.005. As differences in Hansen solubility parameters reflect, the high affinity of co-solvent with PEG and with PES appears to result in lower fouling. Also, weak affinity between co-solvent and water helps maximize the fouling index suppression. The results reported here are significant because they demonstrate that co-solvents can increase the anti-fouling properties of PEG-grafted PES membranes beyond that possible with PEG alone (up to 86% decrease in R) and far better than that with commercial PES membranes (up to 97% decrease in R). Of the four PEG-solvent pairs used to modify the PES membranes, PEG–DMF and PEG–DCM exhibited lower fouling than the others and the control (PEG alone) at the expense of lower permeation flux, while PEG–DCM was the best compromise with respect to anti-fouling properties, permeability, and protein permeation, i.e. maximizing protein capture in the permeate.