Preparation of efficient and durable ultrafiltration membranes based on supramolecular assembly enhanced surface separation method

Abstract

Surface segregation is a practical, cost-effective technique for preparing and modifying ultrafiltration membranes, yet it often involves in the issue of insufficient stability. Due to the similar nature of surface segregation phenomena during membrane preparation and application, the majority of methods that suppress the surface segregation behavior of modifiers during membrane application for better stability also tend to inhibit that during membrane preparation, consequently compromising the initial membrane performance. In response to this issue, we tentatively introduce supramolecular assembly interactions as a means of achieving equilibrium. Specifically, β-cyclodextrin (β-CD) is employed to manipulate the surface segregation behavior of Pluronic F118, a polyethylene glycol based triblock copolymer. First of all, the hydrophily but water-insolubility of β-CD/Pluronic F118 supramolecules effectively curbs the undersegregation and oversegregation phenomenon during membrane preparation and relieves the leaching issue during application. Moreover, the supramolecular assembly of β-CD acts as a nodal role, enhancing hydrogen bonding, hydrophobic interactions, and molecular chain winding among the membrane bulk polymer (polyether sulfone), Pluronic F118, and β-CD. This effect intensifies with closer molecular chain spacing, further boosting the long-term stability of the segregation modifiers. Unlike common hydrophilic modifiers, β-CD does not need to exert its own antifouling property. Instead, it strengthens the surface enrichment and stability of Pluronic F118 through supramolecular assembly. As a result, significant effects can be achieved with minimal amounts of β-CD added. This advancement paves the way for creating highly efficient, durable, and cost-effective ultrafiltration membranes, with potential significant implications for the field of chemical engineering.