Achieving Highly Effective Non-biofouling Performance for Polypropylene Membranes Modified by UV-Induced Surface Graft Polymerization of Two Oppositely Charged Monomers

Abstract

A major problem in membrane technology for applications such as wastewater treatment or desalination is often the loss of membrane permeability due to biofouling initiated from protein adsorption and biofilm formation on the membrane surface. In this study, we developed a relatively simple and yet versatile approach to prepare polypropylene (PP) membrane with highly effective non-biofouling performance. Copolymer brushes were grafted to the surface of PP membrane through UV-induced polymerization of two oppositely charged monomers, i.e., [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropyl methacrylate potassium salt (SA), with varying TM:SA molar ratios. Surface analysis with scanning electron microscope (SEM) clearly showed the grafted copolymer brushes on the membrane surfaces and that with X-ray photoelectron spectroscope (XPS) revealed a similar TM:SA ratio of the grafted copolymer brushes to that of the monomer solution used for the polymerization. Water contact angle measurements indicated that the hydrophilicity of the membrane surfaces was remarkably improved by the grafting of the TM/SA copolymer brushes, with the lowest water contact angle of 27 degrees being achieved at the TM:SA ratio of around 1:1. Experiments for antiprotein adsorption with bovine serum album (BSA) and lysozyme (LYZ) and antibiofilm formation with Escherichia coli (E. coli) demonstrated a great dependence of the membrane performance on the TM:SA ratios of the grafted copolymer brushes. It was found that the characteristics of the surface charges of the membrane surfaces played a very important role in the non-biofouling performance, and the membrane surface with balanced positive and negative charges showed the best non-biofouling performance for the proteins and bacteria tested in this study.

Biofouling of Water Treatment Membranes: A Review of the Underlying Causes, Monitoring Techniques and Control Measures

“…Polypropylene membranes grafted with copolymer brushes through UV-induction of two opposite charged monomers such as [2-(methacryloyloxy)ethyl]trimethylammonium chloride and 3-sulfopropyl methacrylate potassium salt were found to have the ability to resist both protein adsorption and biofilm formation [206]. Poly(ethylene glycol) (PEG) has been shown to improve membrane resistance to nonspecific protein adsorption.…”

Synthesis and Characterization of Poly(ethylene glycol) Methacrylate Based Hydrogel Networks for Anti‐Biofouling Applications

“…Single bacteria strains are commonly used in deposition experiments as favorable indicators for bacteria/surface interactions 40–47. With focus on effects of physicochemical properties onto biofouling, they do not completely exhibit the entire complexity of actual biofoulants (cf 44…”

Polymer Membrane and Cell Models for Drug Discovery

“…By contrast, chemical modification can form a stable membrane surface via grafting molecules by chemical reaction [69,70], plasma [71], radiation [72] and UV [73,74], etc. Various functional polymers can be grafted on the membrane surfaces to improve the hydrophilicity.…”