Preparation And Properties Of Photochromic Hydrogels

Photochromic material is a kind of intelligent material that can change color reversibly in response to electromagnetic radiation.They are used in information storage,anti-counterfeiting materials,molecular switches,and optical printing.For example,naphthopyrans and spirooxazines are photochromic materials with good color rendering,good fatigue resistance,and fast reverse photochromic properties,which make them have wide commercial prospects.However,it is still challenging to introduce photochromic materials into the hydrogel system.In this paper,photochromic materials were introduced into the hydrogel system and their properties were studied,which not only enriches the types of hydrogels but also expands the application range of photochromic materials and hydrogels.With this as the research background,the research contents of this paper are as follows:In the first part,the photochromic materials of naphthopyran were synthesized and introduced into the hydrogel system by doping.The hydrogel was obtained by crosslinking hydroxyethyl methacrylate(HEMA)monomer with a crosslinking agent.The crosslinking agent(AD)was prepared by the interaction of 2-(Dimethylamino)ethyl methacrylate(DMAEMA)and acrylic acid(AA).Density functional theory was used to calculate the process,and the change in Gibbs free energy of the process was less than 0,indicating that the reaction can be carried out spontaneously.In addition,the prepared hydrogel can respond to ultraviolet light in 0.5 s,and it can block part of ultraviolet light,therefore,making it an ideal UV indicator and a raw material for inkless printing paper manufacturing.Due to the presence of freely moving hydrogen ions between the crosslinking agent AD,the hydrogel can conduct electricity,and its conductivity is 0.0042 S/m.In addition,the hydrogel has good compressive resistance and self-healing efficiency up to 59.91 %,and it also shows p H and temperature response.At the same time,the photochromic hydrogel has been successfully made into UV indicator and ink-less printing paper with good results.The second part is the copolymerization of 2-Acrylamide-2-methylpro panesulfonic acid(AMPS)and 2-(Dimethylamino)ethyl methacrylate(DMAEMA)to form a hydrogel,with the incorporation of hydroxylated spiroxazine to give the hydrogel photochromic performance.The polymerization of AMPS and DMAEMA was through electrostatic interaction in the hydrogels.When these monomers combine to form the gel,hydrogen bonding still exists between the polymer chains.Because of these interaction forces,the hydrogels have excellent mechanical properties and remarkable self-healing efficiency up to 73.59 %.Furthermore,the optical properties and electrical healing properties of the photochromic hydrogels were also studied.The interaction between AMPS and DMAEMA produces free moving hydrogen ions,so the hydrogel is conductive.The measured conductivity of the hydrogel is 0.00461 S/m.Owing to the excellent optical and self-healing properties of the hydrogels,they can be used in pattern display devices,which provides a new idea and new direction for intelligent display devices.