Preparation And Research Of Azobenzene/Carbon-based Flexible Devices

Azobenzene can change from trans configuration to cis configuration when stimulated by light and heat,and thus change polarity,molecular length and energy,etc.,which has aroused great interest.However,previous studies often focus on the design and optimization of molecular level.In this thesis,based on the molecular design and selection,and according to the properties of azobenzene molecules,two kinds of flexible devices are designed and prepared,respectively,the flexible photothermal energy storage device and the flexible photo-controlled"mechanical arm"device.（1）3,3’-dimethylazobenzene（AZO-1）and 3-amino-4-4’-dimethylazobenzene（AZO-2）with electron-donating groups,and 4-amino-3-sulfonate sodium 4’-sulfonazobenzene（AZO-3）with electronegative groups,in which AZO-1 is synthesized by oxidative coupling method.FT-IR and ~1H NMR were used to characterize the chemical structure of azobenzene molecules,and UV-Vis absorption spectrum was used to study the light absorption characteristics and photoisomerization performance of azobenzene molecules.TGA results showed that the three AZO molecules had certain thermal stability,which could meet the requirements of thermal stability in practical application scenarios.（2）After the pretreatment of commercial carbon cloth,oxide carbon cloth（OCC）was obtained.AZO-1 and AZO-2 were respectively compound with OCC by solvent evaporation method to prepare AZO-1/OCC and AZO-2/OCC flexible energy storage devices with AZO content of 20%,40%,50%and 60%.FT-IR results showed that no new bond was formed in AZO and OCC composite,and the bond was non-covalent.SEM observation showed that the composite mode of AZO and OCC included AZO attached to carbon fiber surface and AZO filled between carbon fiber.DSC results show that AZO/OCC devices can realize solvent-free energy storage,and the energy storage density of AZO/OCC device includes isomerization energy and phase transformation energy.Under different AZO mass fraction,the energy storage density of 50wt%AZO-1/OCC is the highest（49.5Wh/kg）,and the energy storage density of 50wt%AZO-2/OCC is the highest（58.4Wh/kg）.Enhanced intermolecular interactions（AZO and OCC,AZO and AZO）can improve the isomerization energy of AZO-1 and AZO-2.Because AZO-2 contains amino groups,the interaction between AZO-2and OCC surface oxygen-containing functional groups is stronger,and OCC has a higher degree of enhancement of AZO-2 isomerization energy.AZO/OCC devices have high energy conversion efficiency when the UV intensity is 50m W/cm~2and the irradiation time is 15min.Under the same conditions,the energy conversion efficiency of AZO-2/OCC is greater than that of AZO-1/OCC.In addition,the interaction between OCC and AZO molecules can also improve the thermal decomposition temperature of AZO and enhance the thermal stability of AZO.Bending tests showed that the flexibility of AZO-1/OCC and AZO-2/OCC devices decreased with the increase of AZO mass content,and the flexibility was poor at 60wt%.Considering the energy storage characteristics,thermal stability and flexibility,50wt%AZO-2/OCC energy storage devices have a better application prospect.（3）Using electrostatic assembly,the assembly is formed from the negatively charged AZO-3,the positively charged polymer polydiallyldimethyl ammonium chloride（PDAC）,and the negatively charged graphene oxide（GO）.Then the assembly system is prepared into flexible film by using the mold film forming method.The film can be repaired as a light-controlled flexible"mechanical arm".FT-IR was used to characterize the chemical structure of the molecule,and no new peaks were generated in the film.The presence of Na Cl was characterized by XRD and SEM,which indicated that electrostatic interaction occurred between AZO-3 and PDAC.The results show that AZO-3,PDAC and GO form an"ear of rice"structure by electrostatic assembly,wherein AZO-3 is stably connected to PDAC,GO acts as a nano template,and PDAC is wound and anchored on GO,forming a structurally stable AZO-3/PDAC/GO assembly.AZO-3/PDAC/GO film can undergo phototropic deformation under UV light irradiation,and the degree of deformation is related to UV light intensity and irradiation time.The greater the light intensity,the longer the irradiation time,the greater the deformation degree.The photocontrolled deformation mechanism of the thin film is that,under the stimulation of UV light,the configuration transformation of AZO-3 drives the PDAC molecular chain to move（from point to line）,and the PDAC chain drives the GO template to move（from line to plane）.Transformation of AZO-3 microstructure into macroscopic deformation by point,line and plane integration.AZO-3/PDAC/GO film,as a"mechanical arm",can pull a weight 50 times its own weight when it deformations under 60m W/cm~2UV light irradiation."Mechanical arm"can spontaneously recover after deformation,and blue light can promote the recovery of"mechanical arm"to a certain extent.