Study On Photochromic Gels And Devices

Photo sensitive materials can respond to external light stimulus,they also have been used in many fields such as building materials,biomimetic materials and biomedical materials etc..Photochromic gels,as a type of photosensitive materials,have more and more extensive applications.Many scholars have conducted in-depth research on them.Although photochromic gels have been developed for many years,there are still some shortcomings,such as low responsive speed and single color.In this paper,photochromic gels with fast responsive speed,multi-sensitivity and multi-color response have been successfully designed and prepared.The research work and results are as follows:1.By using N-hydroxymethylacrylamide（NHMA）as monomer,the precursor poly（N-hydroxymethylacrylamide）hydrogels（Nx gels）were prepared by free radical polymerization through the initiation of ammonium persulfate（APS）and tetramethylenediamine（TEMED）.Two preparation routes were investigated:in Route I,the precursor hydrogels were directly immersed in ammonium molybdate（Mo7）solution（that is,the photochromic unit Mo7 was introduced）;in Route II the precursor hydrogels were first dried and then soaked in Mo7 solutions.The experimental results show that the photochromic hydrogels obtained by route II have better photochromic performance.The Nx Moy-II hydrogel prepared by route II can change color obviously under UV for 30seconds.The influence of Mo7 concentrations on the photochromic properties of the gels and the discoloration of the gels in different environments（air,O₂,pure water,and high temperature）were investigated.The hydrogel was characterized by infrared.By the method of photolithography,patterns were printed on the hydrogel,which can be used for information writing and storage.2.Photochromic Nx Moy-II dried gels were obtained from Nx Moy-II hydrogels.These dried gels turned yellow-brown after UV irradiation.The yellowish-brown dried gels turned blue-green after being heated or being put in humid air.These dried gels were characterized by XPS,which confirmed the interconversion between Mo（V）and Mo（VI）during photochromic process.Thermal analysis of the gels showed that condensation reaction occurred at high temperature.The multi-sensitive and multi-color responsive performance of Nx Moy-II dried gels can be used to fabricate devices for colorful information display and storage.3.By using NHMA as monomer and Mo7 as photochromic component and initiator,photochromic hydrogels（iMoxNy hydrogels）were obtained through UV light initiated polymerization.Effects of recipes and polymerization time on hydrogels were systematically studied.This preparation method is simple and efficient,and the obtained iMoxNy hydrogels exhibit excellent cyclic photochromism.iMoxNy dried gels turned yellow after UV irradiation.The yellow dried gel is also sensitive to humid and heat.Based on the gels’multi-sensitivity,the multi-color patterns can be written and stored in iMoxNy dried gels.Furthermore,this preparation method has been proved to be suitable for the preparation of photochromic inorganic/polymer composites with other unsaturated amides as monomers.