Construction Of The New Thermochromic Systems And Research Of Its Discoloration

The development of new performance thermochromic materials helps to expand the range of applications for functional materials to meet the requirements of functional materials in specific areas.At present,the solvent reported in the ternary system is basically a long-chain hydrophobic organic molecule.In this paper,we consider changing the properties of solvents,and explore to separately construct a "bionic" thermochromic system that changes color with ambient temperature and a novel thermochromic system with bistable properties.in the first part of this thesis,we studied the thermochromic system of hydrophilic solvents.First,the color behavior of dye ODBII in a variety of different solvents and the relationship between the color and the electronic structure of the dye molecules are investigated.The color change was confirmed by a large number of experiments and UV-visible spectroscopy tests,and the different electronic structures of the dye molecules and their absorption spectra were verified by DFT.The results showed that the fluoran dye ODBII molecule can exist in three relatively stable electronic structures,that is closed-loop lactone structure,ring-opening zwitterionic structure and ring-opening cationic carboxylic acid structure,and the color of these structures are colorless or white,red and green respectively.Second,the role of the binary or ternary system composed of dye ODBII and hydrophilic organic molecules is explored.The color behavior of different systems was compared between the binary or ternary system of n-alkyl alcohol,alkyl polyol,glycol ethers and ODBII.The results show that the number of hydroxyl groups,the length of the alkyl chain,the polarity of other organic molecules and other factors will affect the proton-donating ability of the alkyl alcohol molecule,which directly affects the electronic structure of the dye molecule,and then influences the hue and depth of the color of the relevant system.At the same time,the formation of intramolecular hydrogen bonds can greatly reduce the ability of organic molecules to give protons,and even make the system appear white.Aboving these,We construct a "bionic" thermochromic system that changes color with ambient temperatureODBII/diethylene glycol ether/1,4-butanediol/HAc,which exhibites green at room temperature of liquid state,and white at low temperature of solid state.We stutied the bistable thermochromic system constructed by phenylethyl phenylacetate derivatives in the second part of this thesis.At the begining,compounds1,2 and 3 were synthesized by esterification of p-hydroxyphenylacetic acid,benzyl chloride,phenylethyl alcohol,benzyl alcohol,benzyloxyphenylethanol and phenylacetic acid.Finally,we constructed a three-component system using compound 1,2 and phenylethyl phenylacetate as solvents,ODBII as a color former and bisphenol AF as a color developer.The results of the thermochromic properties shows that bistable thermochromism exists in all three systems,which means the system is gray or black of solid state below the melting temperature,and system gradually converts to light or colorless transparent solution until the temperature rises to the melting temperature;the system shows a light or colorless transparent solution above the frzeezing temperature,the system gradually changes to a gray or black solid state until the temperature drops to the freezing temperature.