Homoporous membranes of block copolymers: Upscalable preparation by spray coating and performance boosting by quaternization

Abstract

The remarkable permselectivity of homoporous membranes (HOMEs) confers them with unparalleled advantages in high-precision separation. However, the upscalable fabrication of HOMEs remains a challenging yet crucial task to meet practical demands. Herein, we present a facile and controllable strategy for producing HOMEs through spray coating of block copolymers (BCPs) on macroporous substrates, followed by annealing and selective swelling. By controlling the BCP concentrations and ambient humidity during spray coating, dense BCP layers with adjustable thickness can be formed. The use of suitable pore-filling agents for filling the pores of substrates during spray coating and annealing prevents BCP from penetrating into the substrates. Also, it ensures robust adhesion between the BCP layers and macroporous substrates. Direct spray-coating circumvents the intricate and uncontrollable BCP layer transformation process, thereby enabling the successful fabrication of HOMEs over a large area of 100 cm2. The separation performances of thus-prepared homoporous membranes can be easily regulated by changing the swelling durations. Furthermore, the selective swelling process leads to the enrichment of BCP polarity chains on the surface and pore walls, allowing for further quaternization modification. Consequently, a synchronous promotion in permeability and selectivity of HOMEs is achieved.