Studies On The Preparation And Properties Of Polymerizable Thioxanthone Derivatives

Thioxanthone derivatives are a kind of valuable photoinitiators with the advantages of strong ultraviolet absorption,wide peak shape and strong ability to capture hydrogen,and easy to adjust for matching with UV-LED light source.Here,the polymerizable thioxanthone derivatives with coinitiator amine were synthesized to solve the migration and toxicity of thioxanthone and amine,and further improving the efficiency of photoinitiation.2-（3-Diallylamino-2-hydroxy-propoxy）-thioxanthone-9-one（DAHTX）was synthesized from 2,2-dithiobenzoic acid,phenol,epichlorohydrin and diallyl amine.First,a hydroxy-containing thioxanthone（HTX）was synthesized from2,2-dithiobenzoic acid and phenol,and then the epoxy group was introduced by reacted HTX with epichlorohydrin,and finally,DAHTX was obtained by the reaction of diallyl amine with the above.The effects of reaction time,the amount of catalyst and the molar ratio of monomer on the yield of HTX were investigated and find out the optimum reaction conditions:the molar ratio of 2,2-dithiobenzoic acid and phenol is 1:5,the volumn ratio of 1,4-dioxane and water is 4:1,react for 4h in sulfuric acid and N₂.The structures of the products were characterized by ¹H-NMR and FT-IR,respectively.The photophysical and chemical properties of the products were investigated by UV-Vis,PL and RT-FTIR,respectively.The results show that DAHTX has strong UV absorption in the range of 390⁴05nm,the maximum UV absorption peak is at 398.5nm which has a redshift of 5 nm in comparison with that of 2,4-diethyl thioxanthone（DETX）,and the molar extinction coefficient is up to 10⁴.The fluorescence quantum yield of DAHTX and DETX is 0.55 and 0.69 and the mobilities are 6.2%and 17.6%,respectively.This indicates that DAHTX having a rapid intramolecular charge transfers.DAHTX has fast rate of monomer conversion in the early stage of polymerization,and indicates it has the lower decomposition activation energy.The photolysis studies show that it has photobleaching properties.DAHTX has a wide range of solubility,and can dissolve well in alcohol,DMF,dichloromethane,THF and methylbenzene.The DAHTX has good thermal stability with a rapid decomposition in the range of300³50℃.2-methacrylate-2-hydroxyl-3-（methyl-{2-[2-（9-oxygen-9-hydrogen-thioxanthone）-acetic group]-ethyl-}-propyl ester（MAETX）was synthesized from 2,2-dithiobenzoic acid,phenoxyacetic acid,2-（methylamino）ethanol and glycidyl methacrylate.First,O-（thioxanthone-[2]-yl）-oxyacetate（OTX）was synthesized from 2,2-dithiobenzoic acid andphenoxyaceticacid.The9-oxo-9H-thioxanthen-2-yloxy）-aceticacid2-methylamino-ethyl ester（AETX）was synthesized by reacted with 2-（methylamino）ethanol furtherly,and finally,MAETX was obtained by the reaction of glycidyl methacrylate with AETX.The effects of the amount of catalyst,the molar ratio of monomer,the mole ratio of raw material and recrystallization mixed solvent ratio on the yield of OTX were investigated,and find out the optimum reaction conditions:the molar ratio of sulfuric acid and phenoxyacetic acid is 18:1,the molar ratio of phenoxyacetic acid and 2,2-dithiobenzoic acid is 3:1,the volumn ratio of 1,4-dioxane and water is 4:1.The structures were characterized by ¹H-NMR and FT-IR,respectively.The photophysical and chemical properties of the product were investigated by UV-Vis and PL,respectively.The results show that the maximum UV absorption peak of AETX and MAETX are at 395nm and 397 nm,respectively.Both AETX and MAETX have strong UV absorption in the range of 375⁴25 nm,and the molar extinction coefficient is up to 10⁴.The mobilities of MAETX and AETX are 5.8%and 12.1%,respectively.The lower mobility of MAETX is due to the presence of double bonds.The studies on photolysis properties show that both have photobleaching ability.AETX has good sulubilities in water,alcohol and DMF,and MAETX has good sulubilities in DMF,alcohol,acetone and HDDA.The MAETX has good thermal stability with a rapid decomposition in the range of 350³80℃.