Controlled Synthesis of Thin Cross-Linked Films

Cross-linked polymer films are attractive as coatings because they are robust, and ultrathin, imprinted cross-linked films could also serve in real-time, chemically selective sensors. Unfortunately, deposition of thin, controlled cross-linked films is difficult because these polymers are highly insoluble. Growth of such films by in situ polymerization is challenging because polymerization in solution can result in inhomogeneous films or gelation of the reaction mixture. We recently developed techniques for room-temperature film growth by atom-transfer radical polymerization from a surface. Attachment of an -bromocarbonyl initiator to the surface and the use of a very active Cu(I) catalyst allows generation of surface-bound radicals at room temperature and avoids polymerization in solution. This allowed us to synthesize cross-linked films using ethylene glycol dimethacrylate as a monomer. Films are about 50% cross-linked and swelling in solvents is minimal. Future work with this system focuses on imprinting these ultrathin films to yield rapid-response sensors and selective, high-flux membranes.