Composite membranes from photochemical synthesis of ultrathin polymer films

Abstract

THERE has recently been a resurgence of interest in synthetic membranes and membrane-based processes^1–12. This is motivated by a wide variety of technological applications, such as chemical separations^1–7, bioreactors and sensors^8,9, energy conversion^10,11 and drug-delivery systems¹². Many of these technologies require the ability to prepare extremely thin, defect-free synthetic (generally polymeric) films, which are supported on microporous supports to form composite membranes. Here we describe a method for producing composite membranes of this sort that incorporate high-quality polymer films less than 50-nm thick. The method involves interfacial photopolymerization of a thin polymer film on the surface of the microporous substrate. We have been able to use this technique to synthesize a variety of functionalized ultrathin films based on electroactive, photoactive and ion-exchange polymers. We demonstrate the method here with composite membranes that show exceptional gas-transport properties.