Precise surface modification of porous membranes with well-defined zwitterionic polymer for antifouling applications

Abstract

Fouling is a major problem in water treatment membranes. Although surface modification with a zwitterionic polymer is effective for antifouling, precisely controlling the surface state of the modified polymer, considering both polymer chain length and density has not been demonstrated. Herein, we propose a precise surface modification method for water treatment membranes through grafting to approach and evaluate the influence of the graft length and the density of the modifying polymer on the fouling behavior of the membrane. The polymers used to modify the membrane surface were synthesized via atom transfer radical polymerization. Furthermore, the polymer density was controlled during immobilization reaction by varying the solvent type; high-density surface modification was achieved using poor solvents, whereas, low-density surface modification was realized using good solvents. Via this method, poly (2-methacryloyloxyethyl phosphorylcholine) (polyMPC) was successfully modified with controlled densities on porous membrane surfaces with different morphologies. The static and dynamic antifouling properties of the polyMPC-modified membranes were evaluated using the bovine serum albumin solution, and the membrane modified using a higher molecular-weight polyMPC with a higher density was more effective for antifouling. This precise surface control of the membrane can help to rationalize ideal surface characteristics for antifouling applications.