Preparation And Properties Study Of Azobenzene-based Photoresponsive Films

As one of the most typical photoresponsive materials,azobenzene and its derivatives have broad application prospects in the fields of light control drive,photoinduced surface patterning,solar thermal fuel and drug release due to their large molecular size and spectral changes in the process of photo-cis-trans isomerization.Generally speaking,although UV light has higher energy than visable light,its penetration ability to the surface of the object is weak.Therefore,the synthesis of novel azobenzene derivatives and the preparation of functional film materials of moderate thickness are attracted broadly by the majority of scientific researchers.In this thesis,the functional azobenzene-based photoresponsive film was prepared as a starting point.First,a series of azobenzene derivatives were designed and synthesized,and their photoresponsive behaviors were studied.Then,they were prepared into functional films with photoresponsive properties by solvent evaporation and electrochemical deposition,and applied in three fields of artificial mechanical actuator(AMA),photoinduced surface relief gratings(SRG)and solar thermal fuels(STF).(1)Azobenzene-based photo-induced AMA were designed and preparated by supramolecular force between 4,4'-dihydroxyazobenzene and chitosan for the first time.The photoresponsive films were prepared by simple solvent evaporation method due to the intermolecular hydrogen bonding.Under UV light irradiation,the film underwent macroscopic bending rapidly due to the cis-trans isomerization of azobenzene molecules,and lifted 200 times of its own weight.This simple and easy preparation of azobenzene photoresponsive film based on supramolecular interaction provides a theoretical basis for the large-scale industrial production of light control drives.(2)A novel azobenzene based photo-responsive precursor bis-[4-(6-carbazole-9-ylhexyloxy)-phenyl]-diazene was designed and synthesized,which was prepared cross-linked polymer film by electrochemical deposition(ED)method for highly stable SRG application.Due to the cross-linked structure in the ED film,the steric hindrance between molecules was greatly increased,which made the photo-isomerization from the metastable cis conformation to recover to trans conformation difficult,and then the stability of SRG was much improved.The cross-linked ED film was suitable for the application of azobenzene photoresponsive materials in optical information storage under harsh conditions.(3)A series of azobenzene-based photoresponsive precursors with electrochemical active carbazole groups were designed and synthesized,and studied their photo-thermal properties.The bis-[4-(6-carbazol-9-ylbutoxy)-phenyl]-diazene were selected to prepare a cross-linked photoresponsive polymer films by ED method due to the highest energy storage density.The high-quality photoresponsive film can make UV light be used effectively,and realize the preparation of direct-used STF without any pretreatment process.At the same time,due to the high cross-linked degree of the film,the cis conformation azobenzene molecule was more stable,which greatly improved the energy storage life and anti-corrosive property in solutions.It had obvious advantages in daily use,and potential application prospects in self-defrosting glass,self-heating paintings and long-distance solar energy transportation.