Prevention of bacterial adhesion on polyamide reverse osmosis membranes via electrostatic interactions using a cationic phosphorylcholine polymer coating

A simple and easy anti-adhesive coating method against bacteria via electrostatic interaction was developed for polyamide reverse osmosis (RO) membranes using a cationic phosphorylcholine polymer. A commercial polyamide RO membrane was immersed into an aqueous solution of phosphorylcholine polymer containing cationic amino groups, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-2-aminoethylmethacrylate (AEMA)] (p(MPC-co-AEMA)). From the results of contact angle and surface potential measurements, the surface of the coated RO membrane became more hydrophilic than that of raw membranes and had a neutral charge. Conversely, the surface of an RO membrane immersed in an aqueous solution of MPC homopolymer without AEMA groups was not coated by the polymer. Therefore, p(MPC-co-AEMA) was adsorbed via electrostatic interaction between the cationic amino groups of AEMA and anionic carboxylic groups on the polyamide RO membrane. X-ray photoelectron spectroscopy showed the existence of phosphorylcholine groups from p(MPC-co-AEMA) on the coated membranes. The result of quartz crystal microbalance with dissipation monitoring measurements showed that adsorbed p(MPC-co-AEMA) was hardly desorbed from the polyamide surface in a high ionic strength solution at least for one day. The coated RO membrane had high resistance to bacterial adhesion and retained its original rejection performance.