Controlled surface segregation via hydrogel-facilitated phase separation enables uniform TA/PVP layer and in situ silver assembly for high-performance antifouling membranes

Surface segregation during non-solvent induced phase separation (NIPS) enables in-situ membrane functionalization, yet the inherently rapid and uncontrolled phase separation kinetics typically yield heterogeneous additive distribution. Herein, we presented a hydrogel-facilitated phase separation (HFPS) strategy to achieve controlled surface segregation of tannic acid/polyvinylpyrrolidone (TA/PVP) for subsequent in-situ Ag + reduction and assembly of a functional AgNPs layer. By exploiting delayed phase separation kinetics, physical confinement and interfacial gelation imparted by the hydrogel, HFPS yielded substantially higher and more uniform TA/PVP surface coverage (79.8%) compared to NIPS (60.9%). This uniformly enriched TA/PVP layer enabled high-density, homogeneous AgNP grafting with a narrow size distribution on HFPS membranes. The optimized HFPS membrane—with balanced TA/PVP and Ag + loadings—exhibited superhydrophilicity (water contact angle ~ 40°), high water flux (895 L·m −2 ·h −1 ·bar −1 ), and excellent BSA rejection (>98%)—significantly outperforming its NIPS counterpart (50–65°, 362 L·m −2 ·h −1 ·bar −1 , ~ 98%). In dynamic antifouling tests, it achieved a flux recovery ratio (FRR) of 84.7% with BSA filtration and only 5.3% flux decline during bacterial filtration, substantially exceeding NIPS controls (64.4% FRR, ∼45% decline). Moreover, by utilizing patterned hydrogel templates, surface microstructures were introduced to further enhance flux to 994 L·m −2  ·h −1 ·bar −1 and reduce flux decline to 3.8% for bacterial filtration. Ag + release measurements confirmed a higher total Ag loading of 59.1 μg·cm −2 and a stable release rate of 0.199 μg·cm −2 ·day −1 sustained over 40 days. Overall, this HFPS-guided surface segregation strategy offers a promising platform for fabricating high-performance antifouling membranes for engineering applications.