A novel azobenzene-siloxane hybrid material displaying photoinduced macroscopic motions has been prepared by one-step organosilane self-assembly. Two types of alkoxysilane precursors with either pendant or bridging azobenzene groups were synthesized via thiol-ene click reactions. Hybrid films with well-ordered lamellar structures were obtained by hydrolysis and polycondensation of these precursors. The film with solely pendant azobenzene groups showed reversible and rapid d-spacing variation upon UV-vis irradiation, which was induced by the trans-cis isomerization of azobenzene moieties. The flexible, free-standing film obtained by co-condensation of two types of precursors showed reversible bending-unbending motions upon UV-vis irradiation. The partial cross-linking between the siloxane layers by bridging azobenzene groups was crucial for photoinduced distortion of the film. This film possesses high elastic modulus, good thermal stability, and shows large amplitude of photoinduced bending-unbending over a wide temperature range. This is the first report on photoinduced macroscopic motions of azobenzene-containing siloxane-based materials. These materials possess great potential for applications in smart devices and energy conversion systems.

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Lamellar azobenzene–siloxane hybrids were prepared by self-directed assembly of three types of precursors where mono-, di- and triethoxysilyl groups are bridged by azobenzene groups with propylene linkers.

Here, we report a composite film that shows multibending behaviors upon ultraviolet/visible (UV/vis) and near-infrared (NIR) light irradiations. First, an azobenzene-modified graphene oxide (AZO-GO) hybrid was prepared by the covalently grafting of 4-(3-triethoxysilylpropylureido)azobenzene (TSUA) onto the surface of GO. A reversible change in the hydrophilicity of AZO-GO was observed upon UV/vis irradiations, due to the effective trans−cis-photoisomerization of azobenzene groups. Then, the AZO-GO hybrid powder was dispersed in ethanol and homogeneously mixed with the poly(vinyl alcohol) (PVA) aqueous solution to give a uniform and thin composite film (AZO-GO/PVA) with good flexibility by casting. Upon UV irradiation, this film bends rapidly toward the light source with a large amplitude and recovers to the original shape upon subsequent visible irradiation, due to the reversible trans−cis-photoisomerization of azobenzene groups. Upon NIR irradiation, the film curls slightly away from the light source, which is considered to be caused by the photothermal effect of the GO component. This composite film is also low-cost and uses facile manufacturing, with enhanced mechanical properties. Finally, by combining three pieces of the composite films, mimicking the reversible grabbing−release motions of a claw upon UV/vis irradiation was achieved.

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