Preparation And Properties Of Silicone Photoresponsive Materials Based On Azobenzene Structure

In recent years,photoresponsive polymer materials have received widespread attention because,compared with other response behaviors,photoresponse has the characteristics of rapid response,safe and controllable,which can modulate certain specific properties of materials without introducing other disturbances to the system,and the whole process is reversible and basically does not produce by-products,with the advantages of safety,reliability,rapidity and efficiency.These unique advantages make light-responsive polymer materials widely used in the fields of light-responsive microfluidic conductivity,light-responsive biosensors,light-responsive shape memory materials,light-responsive mechanical drive systems,and light-responsive controlled release of drugs.Among the polymers,silicone materials have some characteristics that other polymers cannot have at the same time,such as high and low temperature resistance,weathering resistance,aging resistance,water and oxygen permeability,biophilic activity,and unique reactive properties and low glass transition temperature.They are expected to become a key research target in the field of polymeric photoresponsive smart materials.Azobenzene is one of the more commonly used light-responsive structural units in photoresponsive material systems,which can undergo cis-trans isomeric changes under different light conditions,resulting in changes in dipole moment,polarity,physical geometry and size,and thus causing changes in the overall properties of the material.The research on smart responsive polymer materials is still mainly focused on traditional carbon chain polymers,while the research on organosilicon materials is still in its early stage and there are few related reports.This paper is based on the combination of the advantages of azobenzene structural units and organosilicon substrates,and attempts to study the relationship between structure and properties of azobenzene organosilicon systems.In order to solve the problem of less variety of photo-responsive silicone materials and to facilitate the preparation of photo-responsive silicone materials,this paper selects the isocyanate-based coupling reaction between azobenzene-containing small molecules and common siloxanes to easily and efficiently prepare azobenzene-functionalized siloxane monomers with photo-responsive activity,which have the characteristics of fast response speed,large response amplitude and good reversibility,thus facilitating the introduction of azobenzene The structure of azobenzene was introduced in the corresponding reaction system,which is conducive to the preparation of photoresponsive silicone polymer materials.This paper also explores the preparation of photoresponsive silicone modified nanoparticles,using azobenzene siloxane monomers to modify the surface of silica containing hydroxyl groups to obtain nanoparticles with photoresponsive properties,which have good thermal and humidity stability,easy storage,and potential applications in related fields.Finally,the photo-responsive silicone films based on the azobenzene structure are prepared by the co-hydrolysis method,which can realize the characteristics of photo-induced mechanical deformation motion,photo-induced glass transition temperature change(about 10?)and photo-induced dynamic mechanical property change,and can realize the characteristics of regular and quantitative reversible regulation of energy storage modulus,loss modulus and loss factor,for example.In this paper,the different photoresponse phenomena are characterized and the related response mechanisms are explained:after UV irradiation,the structure of azobenzene contained in photoresponsive silicone films changes from trans to cis in sequence,leading to an increase in the free space volume of chain segments,a decrease in the regularity and glass transition temperature of the system,macroscopic changes in morphology and After white light irradiation or heating,the properties and morphology of the photoresponsive silicone films return to the initial state,thus achieving a reversible cycle.