A new strategy to simultaneously improve the permeability and antifouling properties of EVAL membranes via surface segregation of macrocyclic supra-amphiphiles

Abstract Herein, we propose a new strategy to improve the flux and antifouling properties of ethylene vinyl alcohol (EVAL) membranes by blending with macrocyclic supra-amphiphiles (cyclodextrin; CD). The amphiphilic ‘molecular cage’ geometry of CD, consisting of a hydrophobic cavity segment and hydrophilic rim segment, induces spontaneous surface segregation of CD to form a CD-enriched layer on the membrane surface. The membrane matrix structure was observed by SEM-EDX, wherein elemental composition indicated a gradient distribution of elemental O content from the top to the bottom layer of the cross-section. The layer segregation was governed by the synergistic interactions with hydrophobic and hydrophilic segments of amphiphilic CD polymer during the phase inversion process. When clickable azide-β-CD was fixed into the clickable alkyne-EVAL matrix as a comparative experiment, no surface segregation was observed. The aggregation of hydrophilic CD on the membrane surface increased the surface roughness, hydrophilicity, and water flux (200 L/m2h) of the membrane. Furthermore, the macrocyclic supra-amphiphile-blended membrane showed better antifouling performance than raw EVAL membrane, with a lower water flux decline (21%) and higher water flux recovery (89%). The proposed 3D strategy based on macrocyclic supra-amphiphiles shed lights on the formation of hydrophilic membrane surface with potential applications in membrane technology.