Controlled fabrication and enhanced ultrafiltration performance of porous poly(m-phenylene isophthalamide) hollow fiber membranes via TiO2-assisted pore templating and selective removal.

Poly(m-phenylene isophthalamide) (PMIA)-based hollow fiber ultrafiltration membranes with tunable porosity were developed via a TiO2-assisted pore-templating and selective removal strategy. By varying TiO2 nanoparticle loading (1-10 wt%) and applying controlled hydrofluoric acid etching, the membrane microstructure, permeability, and mechanical properties were systematically tailored. Increasing TiO2 content significantly elevated the dope viscosity, delaying phase inversion and promoting the formation of dense sponge-like structures with thicker selective skin layers. Subsequent TiO2 removal generated additional internal porosity, increasing overall membrane porosity by up to ∼45%, as confirmed by TGA, gravimetric analysis, and SEM-EDS. This structural evolution led to a marked enhancement in water transport, with pure water flux improving by up to 1.88-fold, while maintaining high solute rejection (>95% for bovine serum albumin). The membranes also retained adequate mechanical robustness after etching, sustaining operational pressures up to 3 bar. Importantly, this work demonstrates a sustainable pore-engineering approach that decouples permeability and selectivity by integrating nanoparticle templating with selective removal. The findings provide valuable insight into structure-property relationships in high-performance polymer membranes and offer a potentially scalable strategy for designing chemically robust ultrafiltration membranes that may be applicable to water purification.