Preparation And Properties Of Modulable Photo Controlled Azobenzene Polymer Gel

With the research and development of intelligent sensing materials,more and more scientists are committed to studying the materials with adjustable properties caused by external stimuli,so as to achieve the purpose of making materials show the characteristics required by human beings by applying external stimuli.Azobenzene group is a kind of chemical functional group with high optical application activity.It can realize cis-trans isomerization under the influence of light and heat.According to the characteristics of cis-trans isomerization of azobenzene groups under ultraviolet visible light radiation,scientists introduced azobenzene groups into polymer material systems,and developed a kind of light controllable responsive polymer material systems by adjusting their mechanical properties by applying ultraviolet or visible light.In this dissertation,4,4 ’-dihydroxy azobenzene was synthesized by coupling diazotization reaction,and then hydrophobic alkyl long chain and acrylamide groups were introduced by substitution reaction to synthesize the final monomer molecule.First,the physical interaction between Azo-2 monomers is studied.The results show that Azo-2 molecules can form organic gels in toluene solution based on the stacking of the azo phenyl group,the hydrophobic interaction of alkyl chains and the hydrogen bonding of amide groups.The conversion of gels to sols can be achieved after UV irradiation or heating up to 70 degrees Celsius.When visible light is irradiated or cooled to room temperature,the sol to gel transition is achieved,resulting in the formation of a photo rheological fluid to achieve the purpose of adjusting the viscosity of the solution.It can be applied to the combination of highly efficient heat transfer and drag reduction agents to regulate microfluidic flow and controlled encapsulation and release.In addition,because the Azo-2 monomer has good solubility in water and can be polymerized in water,Azo-2 is dissolved in polyvinyl alcohol(PVA)aqueous solution,initiator and crosslinking agent are introduced,and Azo-2 is cross-linked and polymerized in water,and then through freezing and thawing,a hydrogel with interpenetrating network is formed,which has hydrogen bonding interaction between PVA and water and Azo-2 polymerization crosslinking.In contrast,the pure PVA hydrogel and Azo-2 and PVA mixed water gel materials were prepared to study the performance changes caused by UV visible light.Through experiments,it is found that the storage modulus G’ of pva-pazo-2 gel is always greater than the loss modulus G’’,the tensile fracture stress is 0.80 MPa,the fracture strain is 251%,the maximum compressive stress can reach 11 MPa and the maximum compressive strain can reach90%,which has excellent tensile property,resilience and compression stability.PVA-PAzo-2gel hydrogel material has good electrical conductivity,plasticity and excellent mechanical properties,and will produce transparency and flexural extension response after ultraviolet visible light irradiation.It adds many possibilities for the application of azobenzene hydrogel.It can be applied to strain sensors,wearable sensors,photo actuators,etc.In the design of materials and devices such as photo-transparent films.