Synthesis And Application Of Triarylsulfonium Salts As Photoinitiators

UV-curing technique developed in recent years,which possesses advantages of short-curing time,simple equipments and eco-friendly is widely used in coatings,printing inks,varnishes,painting,electronics and packaging materials.In normal conditions,a photopolymerization system is comprised of an oligomer or a reactive monomer,a photoinitiator and optional additives.The photoinitiator plays an important role only about 5% in the photo-curing and photopolymerization since it determines the photopolymerization speed and affects polymer properties such as yellowing,odor,migration,and etc,which is paid more attention by scholars.In this paper,we synthesized a series of photoinitiators of benzothiophene and triarylsulfonium salts according to related literature characterized by 1H NMR,13 C NMR,HPLC,UV-Vis and MS etc.The details as follows:On the one hand,the benzoylbenzothiophene derivatives(7),Friedel-Crafts acylations,were synthesized by 5-methyl-3-phenyl benzothiophene(6)and benzoyl chloride under different heating conditions;several S-benzothiophene salts(8)were obtained by diaryliodonium trifluoromethanesulfonates and benzothiophene with Cu(OAc)2 as catalyst,dramatically,which is a solvent-free reaction,then happened ring-opening to get 9 that 2-ethinyl diphenyl sulfide as the parent in the environment of alkaline sodium ethanol.The conditions included the kind and amount of catalysts,solvent as well as reaction time of 5-methyl-3-phenyl benzothiophene(6)were optimized.It concluded that the perfect oil-bath heating experimental conditions are in CH2Cl2 solvent with the reaction time of 12 h and n(5-methyl-3-phenylbenzothiophene):n(Benzoyl chloride): n(AlCl3)=1:1.2:2.4;the perfect MW heating experimental surroundings are in DMF solvent with the reaction time of 20 min in the power of 30 W;The target products in different heating approaches characterized by HPLC to conclude that the latter is superior to the former.Subsequently,the final compound 7 was measured by coating preparation and film property test,m(compound 7):m(Irgacure 184)=1:1,the adhesion improved to level 1,the hardness improved to 4H,which turned out the characters of compound 7 than BP and Irgacure 184 used widely in curing speed,hardness and adhesion.The product 7 was selected as an example for the possible polymerization mechanism.On the other hand,the triarylsulfonium salts(10,11)were synthesized by the reaction of diaryliodonium trifluoromethanesulfonic salts and dibenzothiophene or 4-(S-tolyl)benzophenone(BMS)with different catalysts.The two kind of compounds 12 a and 12 b were get in one step synthesis of two compounds though 2-mercaptobenzoxazole and 1,4-diiodobenzene,then the compounds 13 a and 13 b were sythesised by the reaction of trifluoromethanesulfonic salt and 12 a and 12 b.The conditions included the kind and amount of catalyst,solvent as well as reaction temperature of 10 a,11a and 13 a were optimized.It concluded that the perfect experimental conditions of 10 a are with the reaction temperature of 130 °C and 10 mmol% Cu(OAc)2 as catalyst,11 a in 1,1,2,2-Cl2CHCHCl2 solvent with the reaction temperature of 110 °C and 10 mmol% CuI as catalyst,13 a in 1,1,2,2-Cl2CHCHCl2 solvent with the reaction time of 2 h,the reaction temperature of 110 °C and 10 mmol% CuI:Cu(1:1)as catalyst.The target compounds were characterized by 1H NMR,13 C NMR,UV-Vis and MS etc.The UV-maximum absorption wavelength of 10 a from the UV spectrum shift to red.Subsequently,the final compound 10 and 11 were measured by coating preparation and film property test,all the curing film are smooth and transparent,which turned out the characters of 10 and 11 than BP and Irgacure 184 used widely in curing speed,hardness and adhesion.Finally,the product 10 a was selected as an example for the possible polymerization mechanism.