Downstream Monomer Capture and Polymerization during Vapor Phase Fabrication of Porous Membranes

Porous membranes can be formed by the polymerization of solid monomer by a vapor-phase initiator followed by sublimation of the unreacted monomer. This versatile bottom-up process can be used to deposit porous polymer membranes on a variety of substrates including planar, curved, and structured surfaces. In this paper, we incorporate additional thermoelectric coolers (TECs) into the reactor in order to study downstream monomer capture and polymerization. Better uniformity across the TECs is achieved by capturing the unreacted monomer from the preceding surface instead of capturing the monomer onto multiple surfaces at once. We show that the surface temperature of the downstream TEC affects the membrane morphology and the kinetics of polymerization. Lower capture temperatures lead to better surface coverage while higher temperatures promote the polymerization rate. The morpho-logical differences are further confirmed by coating the membranes with a fluoropolymer to study variations in hydrophobicity. Our ability to capture and polymerize monomers across multiple TECs provides a sustainable route for enhancing the throughput of the process which is desirable for practical applications.