A Novel Method for Manufacturing Membranes with Ultra-Thin Hydrogel Selective Layers for Protein Purification: Interfacially Initiated Free Radical Polymerization (IIFRP)

Hydrogels are promising materials as membrane selective layers due to their fouling-resistant nature, tunable mesh size, and functionalizability. These features are especially critical for protein purification applications. Yet, the fabrication of thin, uniform hydrogel membrane selective layers using a simple, scalable process is an unmet challenge. We demonstrate a novel method, interfacially initiated free radical polymerization (IIFRP), for fabrication of ultra-thin hydrogel selective layers on porous supports in a simple and reproducible process. This method utilizes segregation of the monomer and the photoinitiator into two separate, immiscible phases to form a very thin, uniform and defect-free hydrogel layer at the interface upon photopolymerization. The resulting hydrogel-coated membranes have selective layers as thin as <100 nm, and can separate the proteins based on their size with a sharp molecular weight cut-off. The method is readily tunable for a broader range of separations simply by altering experimental parameters (e.g. UV exposure time, monomer concentration) or addition of inert porogens/comonomers. Membranes prepared using this method exhibit extremely high anti-fouling properties upon extended exposure to protein solution providing a promising approach for protein purification. These membranes can also be manufactured to include various nanomaterials such as catalytic nanoparticles. Taken together, these findings illustrate a significant step toward simple, robust and scalable fabrication of ultra-thin, functional hydrogel selective layers in a controlled manner, with potential applications in bioseparations, wastewater treatment, and gas separation.