PHOTORESPONSIVE MONOLAYERS CONTAINING IN-CHAIN AZOBENZENE

Azobenzene monolayers on silicon have been prepared by two synthetic m ethods: (1) chemisorption of triethoxysilanes, and (2) acylation of am ine-functionalized self-assembled monolayers with acid chloride deriva tives. A series of films were prepared with different methylene spacer lengths and different, terminal end groups (pentyl vs hydrogen). The resulting films were characterized using water contact angles, X-ray p hotoelectron spectroscopy, attenuated total reflectance infrared spect roscopy, and X-ray reflectivity (XR). Despite evidence for successful attachment of azobenzene to the surfaces, film thicknesses as determin ed by XR suggest uniform, but incomplete, monolayers. Irradiation of t he films with 354 nm light effected a decrease in the water contact an gle. The largest photoinduced changes in contact angles (9 degrees) we re observed for films prepared by acylation and with terminal pentyl g roups; for one of these films, XR monitoring of film thicknesses showe d a 1 Angstrom increase in film thickness during 354 nm irradiation.