Strategic Dual Cross-Linking of Partially Quaternized Membranes Containing Dangling Alkyl Spacers for Enhanced Anion Selectivity with Antibacterial and Antibiofouling Properties

We investigated the Cl – / S O 4 2 − permselectivity and antibacterial properties of polyvinylidene fluoride- g -poly[2-(dimethylamino) ethyl methacrylate] (PVDF- g -PDMAEMA)-based anion-exchange membranes (AEMs) prepared by a nonsolvent induced phase inversion process. In this work, we assessed the contribution of the chain length of the quaternizing agent using two distinct alkyl spacers: methyl (C 1 ) and decyl (C 10 ) groups, followed by dual cross-linking. The dual-step cross-linking process included in situ cross-linking achieved individually with xylene dichloride (XDC) or poly(methyl methacrylate)- co -poly(chloromethylstyrene) (PMMA- co -PCMSt), followed by surface cross-linking using N, N, N ′, N ′-tetramethyl-1,6-hexanediamine (TMHDA). Thus, the impact of a small molecular cross-linker (XDC) and a polymeric cross-linker (PMMA- co -PCMSt) on the selectivity of the membranes was studied. Among the four dual-cross-linking network-architected robust membranes, the representative PD C membrane, featuring a C 10 side chain and dual cross-linking with PMMA- co -PCMSt and TMHDA, achieved a remarkable Cl – / S O 4 2 − permselectivity value of 28.25 using a 0.05 M NaCl + 0.05 M Na 2 SO 4 mixture. Additionally, this membrane demonstrated outstanding antibacterial efficacy against E. coli and B. subtilis, with 99.9% bacterial inhibition (BI) in each case. Dynamic biofouling studies showed that the PD C membrane retained better performance, with only a 55% decline in desalination efficiency after five continuous cycles, compared to 67.9% for the commercial Ionsep AEM, highlighting its superior antibiofouling properties.