Synthesis of photoactive compounds for surface modification (e.g. SiO2)
Depending on the desired application, the surface characteristics can be tailored. In the frame of a BMBF funded project (OSOKA, FKZ 16SV3537) azobenzene compounds were synthesized for photo-controllable surface modification. The cis/trans isomerization of the diazo group allows changing the surface characteristics by irradiation at a certain wavelength. Different azobenzene based organosilanes were investigated with different functionalities.
Currently, a photo-induced reversible contact angle change with diiode methane of 5° was observed by non-substituted thiol compound. For photoswitchable compounds with different functionalities and silane anchor, contact angle changes with water in oil of 6°-8° can be achieved. The activation energy for photoisomerization was calculated by the Arrhenius equation.
Left. Series of UV/vis spectra of azobenzene with silane anchor with simultaneous irradiation at lambda = 350 nm. The diazo group switches from the trans (black spectrum) in the cis state.
Right. Reversible molecular switch at different wavelength¸ irradiation at lambda = 350 nm and 445 nm.
[1] | S. Möller, U. Pliquett, C. Hoffmann, Synthesis of molecular photoswitches based on azobenzene with organosilane anchor, RSC Advances 2 (11/2012) 4792–4801. |