Abstract:
” A polysaccharide-based smart photo-actuator is fabricated via electrospinning of cellulose 4-phenyl azobenzoate (Azo-Cel) from its organic solution in a mixture of high-volatile acetone, a poor solvent of Azo-Cel, and low-volatile N,N-dimethylacetamide (DMAc), a good solvent of Azo-Cel. Stable electrified polymer jets are generated at an ideal polymer concentration (17 wt%) and solvent mixing ratio (acetone/DMAc = 3/2 (v/v)) so that continuous nanofibers can be drawn on a cylinder-shaped rotating drum electrode under a strong electric field (25 kV) and the non-woven fabric can be produced. The Azo-Cel fabric is confirmed to be made up of uniaxially aligned nanofibers via scanning electron microscopy. The water contact angle of the Azo-Cel fabric reversibly decreases and increases in response to alternate irradiation with UV and visible light to geometric deformation of the azobenzene moiety between the trans and cis isomers, resulting in lower and higher surface free energies, respectively. Furthermore, self-standing Azo-Cel fabric shows a photomechanical asymmetric bending deformation toward the light source caused by UV light. Regioselectively functionalized Azo-Cel was synthesized through protection of C6 of AGU by tritylation, then esterifying the C2 and C3 regions, then eventually deprotecting the C6 regions to obtain di-Azo-Cel. Although this method shows no change in WCA of the new product compared to Azo-Cel, the photo-responsive bending is heavily impacted and dampened probably due to a molar decrease of functionalized Azo side groups and the presence of –OH groups that form intramolecular hydrogen bonds.”
