In situ UV-photopolymerization of gas-phase monomers for microanalytical system applications

Abstract

The controlled growth of thin polymer films by in situ UV-photopolymerization of vapor-phase monomers in the absence of a photoinitator is described and the use of this process for integrated sensor-array interfaces, etched-channel separation column stationary phases, and passivation layers within microanalytical systems designed for the determination of gases and vapors is considered. Following preliminary tests with methylmethacrylate, attempts were made to grow polymer films from four commercial silylated methacrylate monomers on substrates of silicon, glass, and/or ST-quartz. Continuous films of poly[(trimethylsilyl)methylmethacrylate] (PMTMS) and poly[(phenyldimethylsilyl)methylmethacrylate] (PMPDMS) were grown to thicknesses of ∼30–300 nm, while attempts to grow films of poly[((tris-trimethylsiloxy)silyl)propylmethacrylate] and poly[propylsilatranylmethacrylate] were unsuccessful. Chlorotrifluoroethylene was used to grow films of potential use as passivation layers. Films of PMTMS were patterned using a quartz photomask with 300 μm lines and spaces, and were grown on vertically aligned substrate surfaces, as models of high-aspect-ratio etched-channel walls. PMTMS and PMPDMS films were then grown directly on working 250 MHz SAW resonators subsequently exposed to a series of organic vapors. Response profiles, calibration curves, and relative response patterns were examined. Results, though mixed, demonstrate the feasibility of this approach for producing polymer thin films for microanalytical system development.