Photochemical Generation of Light Responsive Surfaces

The preparation of patterned photoswitchable surfaces by employing the nitrile imine-mediated tetrazole ene cycloaddition (NITEC) photoinduced reaction in the presence of dipolarophiles based on photoresponsive azobenzene moieties is reported. The dipolarophile used is a maleimide carrying either an azobenzene unit or a first generation dendron containing two azobenzene units. X-ray photoelectron spectroscopy (XPS) is employed to analyze the functionalized silicon wafers, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) evidences the spatial control of the functionalization of the surface achieved by using a micropatterned shadow mask. Water contact angle measurements and optical inspection observing the behavior of a water droplet demonstrate the photoinduced change on wettability of the structured functionalized surfaces due to the reversible trans-to-cis isomerization of the azobenzene moities.