Preparation And Characterization Of Sulfur-containing High Refractive Index Materials By Mercaptan-ene Reaction

Compared with inorganic optical materials,optical resin has the characteristics of light weight and impact resistance,and the higher refractive index optical resin can reflect the advantages of miniaturization and lightweight.All kinds of optical resins with high refractive index are being studied at home and abroad.According to the relationship between the refractive index of polymers and the molar refractive degree of atoms or groups,the introduction of aromatic compounds,heteroelements such as sulfur,nitrogen and phosphorus,and halogen elements except fluorine can improve the refractive index of materials in varying degrees.Among them,the introduction of sulfur can effectively increase the molecular refractive index and cause small dispersion,which is one of the research hotspots in recent years.Mercaptan-olefin click chemical reaction has the advantages of rapid reaction,mild conditions and single product,so this paper chooses mercaptan-olefin click chemical reaction to synthesize high refractive index optical polymer.In this paper,2,5-bis(p-aminophenylthio)thiophene(APST)was synthesized from 2,5-dichlorothiophene and 4-aminothiophenol by nucleophilic substitution reaction and recrystallized with ethanol.The carbamido-containing binary olefin monomer 2,5-bis(4-[3-{2-(2-en-2-methylpropionyloxy)ethyl} carbamido] phenylthio)thiophene(X1)was synthesized by nucleophilic addition reaction of APST with isocyanate methacrylate.The binary olefin monomer2,5-bis(4-[2-acrylamido] phenylthio)thiophene(X2)containing amide group was synthesized by nucleophilic substitution reaction of APST with acryloyl chloride.The effects of different reaction conditions on the yield of each product were compared,and the reaction conditions were optimized.The structures of the products were characterized by FTIR,NMR and elemental analysis.Carbamido polythioether PTEC and amide polythioether PTEA were synthesized by thiololefin click chemical reaction of X1 and X2 with 2,5-disulfanyl-1,4-dithiane(DSDT),respectively.The structure,molecular weight and distribution,thermodynamic and optical properties of PTEC and PTEA were characterized by FTIR,NMR,GPC,TGA,DMA,DSC,UV-vis spectrophotometer and ellipsometer.The results show that the two polythioethers have good thermal stability.The 5%thermal decomposition temperatures of PTEC and PTEA are 244℃ and 258℃ respectively,and the glass transition temperatures measured by DMA are 85.9℃ and 111.3℃ respectively.They have high mechanical strength,and the storage moduli of PTEC and PTEA measured by DMA at room temperature are 1350 MPa and 2070 MPa,respectively.They also have excellent optical properties,in which the refractive index of PTEC is 1.682,Abbe number is 26.4,the transmittance at 400 nm is more than 95%,the refractive index is 1.711,Abbe number is 21.2,and the transmittance at 400 nm is 92%.