Design,Synthesis And Application Of Photoresponsive Azo Polymer Materials

Stimuli-responsive materials have attracted extensive attention for their environmental responsiveness,molecular transition control,and energy conversion between interior and exterior.Stimuli-responsive materials show great potential in various fields,especially in optoelectronic applications,such as self-adaptation,intelligent detection,information storage,camouflage and anti-counterfeiting recognition,soft robotics,drug release,etc.With the gradual deepening of people's understanding of the response mechanism and the continuous expansion of the types and properties of smart materials,the development of related fields has been greatly promoted.However,in order to meet the needs of practical applications,it is still necessary to design and develop novel structural responsive materials to improve and perfect the relevant properties of the materials.In this paper,based on the relationship between the structure and properties of light-stimulated responsive switching materials,we designed and synthesized azobenzene molecules with new structures,and studied their properties and application prospects.The details are as follows:In the first chapter,we mainly introduce the classification and action mechanism of stimuli-responsive molecular switch materials,focusing on the development and application of azobenzene-based materials,and discuss their application,development status and the main problems in various fields.On this basis,the idea of this paper is drawn.In the second chapter,we designed and synthesized a photochromic material based on azobenzene structure and applied it to the field of rewritable paper by simple dip coating.Among them,the introduction of hydroxyethyl methacrylate increased the bonding force between the material and the paper.Due to the formation of intermolecular hydrogen bonds,the conversion time of photoisomerized azobenzene molecules from the thermodynamically unstable cis isomer to the stable trans isomer is greatly increased,thereby improving the color retention time of rewritable paper(>48 h).The color of the rewritable paper can be changed from yellow to red within 1s under the irradiation of ultraviolet light,and the color can be quickly erased at80?/min.After 10 times of erasing,it still has good quality erasing capability.The rewritable paper is simple to prepare,suitable for large-area preparation,has high resolution(<5 ?m),and has good storage stability,which is favorable for realizing industrial application in the erasable and rewritable field.In the third chapter of the thesis,we increase the flexibility of the chain segment by introducing a long alkyl chain on the azobenzene molecule,so that the azobenzene molecule can complete the transformation of cis-trans isomerization more quickly under ultraviolet light.At the same time,the introduction of trifluoromethoxy makes the surface energy of cis and trans structures very different,and the introduction of high fluorine-containing acrylate amplifies the change of molecular surface energy due to cis-trans isomerization of azobenzene molecules.The wettability change from highly hydrophobic(CA > 130°)to superhydrophilic(CA = 0°)under light was successfully achieved on the filter paper substrate,and the change process could be completed within 10 s of UV light.Further,we used different photomasks to obtain various patterns of hydrophilic and hydrophobic regions,and the various hydrophilic and hydrophobic regions can be converted to each other.Affected by the hydrophobic defects on the surface of the filter paper,the sliding angle of the film to droplets can also be reduced from 180° to 90° under UV light irradiation.Finally,we have successfully achieved the transfer and actuation of specific droplets by selective UV light irradiation.The characteristics of precise control of the reaction site and the time of participating in the reaction may further expand the application of this type of materials in the field of microfluidic technology and selective drug release.In the fourth part of this paper,we designed and synthesized three types of stimuli-responsive optical waveguide composites,and explored the effect of different responsive molecules on the refractive index of the material at different positions in the polymer.First,we synthesized a backbone-type azobenzene polycarbonate optical waveguide material based on azobenzene monomers modified by alkyl chains.The material has good thermal stability,and the refractive index change before and after irradiation is as high as 1.5%;then based on epoxy-modified azobenzene molecules,we copolymerize it with Su-8 epoxy resin to obtain a side chain azo benzene epoxy resin.The polymer optical waveguide material has good thermal stability,and the resin shows a more sensitive refractive index change than the main chain azobenzene optical waveguide material under ultraviolet light irradiation.At the same time,we also studied the reversible variation of the refractive index of the polymer side chain with different contents of azobenzene with ultraviolet light,and this kind of material is more suitable for the preparation of fast-response optical waveguide devices;Finally,we obtained a polycarbonate optical waveguide material that can be photocrosslinked in the absence of an initiator through the modification of cinnamoyl groups.The 5% thermal weight loss temperature of the material can reach 400?.On the one hand,compared with the Su-8 material,the cinnamoyl-terminated polycarbonate material introduces C-F bonds to replace the C-H bonds,and on the other hand,the absence of initiator reduces the residue of small molecules after curing,which makes the absorption loss of the material at the communication window 1550 nm and 1310 nm is lower.The materials can be used as carriers of azobenzene structures and have potential application prospects in the field of optical waveguide devices requiring low optical loss.