Preparation And Characterization Of Azobenzene Modified Graphene Oxide/Polyvinyl Alcohol Photoresponsive Composite Films

Stimuli-responsive polymer composites can receive stimulation signals from the external environment,change their macromolecular structure or state,and then affect their properties and show corresponding functions.Photo-response has attracted extensive interest of researchers because of its advantages of remote control,environmental protection and non-pollution,and local operation of responsive materials.Azobenzene is a representative of a class of light-responsive compounds that can undergo reversible cis-trans isomerization(trans-cis)inside its molecules when exposed to ultraviolet-visible light.Graphene oxide is rich in oxygen-containing functional groups on its base and edges,so it has good thermal conductivity,excellent light-to-heat conversion performance,etc.,and is introduced into the molecular structure to improve the performance of composite materials.Azobenzene-containing silane precursor covalently modified graphene oxide has a wide application prospect in anticorrosive materials,photoelectric materials and so on.In this thesis,utilizing the reversible cis-trans isomerization response of azobenzene groups under UV/Vis irradiations and the excellent photothermal effect of graphene oxide,triple-photo-response of azobenzene modified graphene oxide /polyvinyl alcohol(AZO-GO/PVA)composite film was realized.The specific research is as follows:(1)4-(3-Triethoxysilylpropyl urea)azobenzene(TSUA),a precursor of azobenzene-containing silane,was synthesized,and the optimal hydrolysis conditions of TSUA were investigated.The molecular structure of TSUA before and after hydrolysis was characterized by FT-IR.The reversible photo-isomerization of azobenzene groups was confirmed by UV-Vis absorption spectra.(2)Graphene oxide(GO)was synthesized by an improved Hummer method.The functional groups on the surface of GO were identified by FT-IR.making it possible for the subsequent covalent modification.The hydrophilicity of GO was identified by contact angle test.AZO-GO was synthesized by covalently grafting the azobenzene-silane precursor to GO surface after hydrolysis of alkoxy group.The molecular structure of AZO-GO was characterized by FT-IR.The reversible photo-responsive property of AZO-GO was confirmed by UV-Vis absorption spectra.(3)Polymer-based composite films with different mass fractions of AZO-GO were prepared by blending the above synthesized AZO-GO with PVA and casting the mixtures on substrates.The mechanical strength of the composite film with 1.5wt%AZO-GO was significantly higher than that of pure PVA film.The 1.5wt%composite film can achieve a triple-response to UV/Vis and NIR light irradiations.Under UV/Vis irradiations,fast and reversible bending-unbending motions with large amplitudes were realized,rendering it potential application as photo actuators.