Fabrication of a smart self-cleaning PES membrane using PMMA-co-PVP responsive zwitterionic copolymer with biocidal properties

In this study, a responsive zwitterionic copolymer (RZC) based on polymethyl methacrylate-co-polyvinyl pyrrolidone (PMMA-co-PVP) was synthesized via free radical copolymerization and incorporated into a polyethersulfone membrane matrix. This modification significantly enhanced permeability from 22.1 to 220.03 LMH.bar⁻¹ at pH 7, and from 21.9 to 254.3 LMH.bar⁻¹ at 45 °C. RZC-modified membranes showed higher removal rates of BSA (97.3 to 99.7 %) and amoxicillin (40.7 to 90.4 %) compared to the bare PES membrane. The removal rate of yellow, black dyes, and heavy metals Ni²⁺, Pb²⁺, and Cr³⁺ increased from 91.2 to 93.9, 91.3 to 93.5, 64 to 93, 56 to 100, and 30 to 65 %, respectively. Analysis of membrane response under varying pH and temperature conditions revealed the emergence of a smart gating feature attributed to copolymer memory and supported by high flux and minimal fouling. Surface free energy analysis of membrane-fouling interactions and antibacterial performance revealed enhanced biofouling resistance due to foulant removal by the hydration shell. Additionally, methyl methacrylate exhibited bactericidal effects of up to 46.98 % against S. aureus and 39.43 % against E. coli. Strong chlorine resistance, non-leaching behavior, and long-term flux stability highlight the membrane's potential for scale-up. These advantages are attributed to the RZC's crystalline nature, planar structure with high surface area, relatively high molecular weight, excellent thermal stability, uniform distribution across the membrane surface and pores, reduced surface roughness, enhanced mechanical strength, and responsive smart properties. Accordingly, RZC presents a promising alternative for developing self-cleaning membranes to control biofouling in low-pressure filtration systems.