Self-assembled monolayers on polymer surfaces:: Kinetics, functionalization, and photopatterning

Monolayers of bifunctional bolaamphiphiles were self-assembled on a polymeric substrate (spin-coated film of poly(allylamine hydrochloride)). Various features of the novel bifunctional, well-ordered, and relatively stiff monolayer and the subsequent reactions of the exposed benzoyl azide groups were investigated. The characterization of the monolayers and the kinetics of self-assembly was determined via reflection-absorption infrared spectroscopy and ellipsometry. Atomic force microscopy and ellipsometry were used to measure roughness and thickness, respectively. From molecular modeling and ellipsometry, the bolaaphiphiles in the monolayers were found to be inclined at an angle of about 68 degrees to the normal. In addition, the monomolecular layers appeared to be fairly crystalline. Serial functionalization of the exposed benzoyl azide groups with dansyl-cadaverine in the liquid phase followed by propylamine in the gas phase illustrated a stable, dense, well-ordered, two-dimensional monomolecular layer of bolaamphiphiles. Photopatterning, via UV irradiation of exposed benzoyl azide groups, was also demonstrated. The novelty of the surface modification procedure described here is the extraordinary ease with which self-assembly took. place and the stability of the resulting monolayers which formed a highly reactive new surface suitable for further modification. Arranging molecules in a tidy ordered array on a polymeric surface is a main result of this work.