Unraveling Phase-Selective Fouling of PVDF Membranes: Molecular Mechanisms from Simulation and Experimental Verification

Membrane fouling critically limits the separation performance of poly(vinylidene fluoride) (PVDF) ultrafiltration membranes, a process inherently linked to the polymer’s crystalline structure. The dominant α (nonpolar) and β (polar) phases present distinct interfacial properties, yet their specific roles in governing foulant adhesion remain unclear at the molecular level. This knowledge gap hinders the rational design of phase-engineered antifouling membranes. Herein, molecular dynamics simulations and filtration experiments were integrated to unravel the mechanisms of crystalline phase-dependent fouling. Three representative foulants, bovine serum albumin (BSA, protein), dextran (polysaccharide), and alginic acid (polyelectrolyte), were investigated. Simulations reveal that adsorption is predominantly driven by van der Waals forces, with interaction strengths following the order BSA > dextran > alginic acid. Crucially, a distinct phase selectivity emerges: BSA exhibits stronger affinity for the α phase, whereas dextran and alginic acid favor the β phase, a phenomenon governed by differences in interfacial hydration structure. These molecular-level predictions were broadly supported by experimental fouling trends and resistance analysis. Our work suggests a likely causal relationship between the PVDF crystalline phase and foulant-specific adsorption, which may offer a useful mechanistic basis for designing PVDF membranes with tailored phase composition to address targeted foulants in water treatment.