Study On Preparation And Application Of 2,3-Bis((2-Mercaptoethyl)Thio)-1-Propanethiol

Thiol click chemistry has been focused on because of its high efficiency and versatility.Polymercaptan have been widely used in the synthesis of medium and high refractive index polythiourethane optical resins.Among them,2,3-bis((2-mercaptoethyl)thio)-1-propanethiol(GST)is one of the main raw materials for polythiourethane lenses in the market currently.However,the domestic GST compared with foreign has low purity and high chromaticity,self-production capacity needs to be upgraded at present.And it was found that the polythiourethane produced by the thiol-isocyanate(SH-NCO)click reaction had the problem of brittleness.The main research of this paper are as follows:(1)Using 1,3-bis((2-hydroxyethyl)sulfanyl)propan-2-ol and thiourea as raw material,isothiourea salt was prepared and GST was obtained through hydrolysis.It was found that the concentration of 1,3-bis((2hydroxyethyl)sulfanyl)propan-2-ol(ypolyalcohol)synthesized by one-step method influenced the synthesis of GST.Therefore,in order to improve the concentration of GST(yGST),the dropping time(tECH)and reaction temperature(TECH)of ECH,ωNaOH,NaOH/ECH and β-ME/ECH molar ratio(nNaOH:nECH,Nβ-ME:nECH)on it were studied,and the process were optimized.Under the optimum conditions,the liquid phase normalized content of 1,3-bis((2hydroxyethyl)sulfanyl)propan-2-ol reached 97.34%.After studied the influence of the process parameters of 1,3-bis((2-hydroxyethyl)sulfanyl)propan-2-ol,we determined that ypolyaicohol obtained by the optimum conditions can produce GST with the best quality which liquid phase normalized content and chromaticity were 94.08%and 15.The optimum conditions was that:tECH was 150 min,TECH was 20℃,ωNaOH was 30 wt%,nNaOH:nECH was 1.15:1,nβ-ME:nECH was 1.96:1.Then,structures of GST,byproducts of mono-substituted and tri-substituted thiol were tested through liquid chromatography-mass spectrometry.(2)The polythiourethane was modified through introducing ene monomer into the thiol-isocyanate dual networks.The doping of thiol-ene(SH-C=C)increased the crosslinking density,meanwhile,the formation of flexible sulfide bonds and the reduction of polyurethane groups decreased the rigid radical of the polymer networks.The modified elastic polyurethane(TPU)had good thermal,mechanical and optical properties with significantly increased impact toughness.As to GST-TATAT-XDI,when the molar ratios of C=C/NCO were 50/50 and 30/70,the impact strength of the modified UV-heat dual-curing TPU was increased by 286.56%and 158.39%,respectively,compared with GST-XDI without added ene.The effects of the molar ratio of thiol,isocyanate monomer and C=C/NCO on the thermal,mechanical and optical properties were studied,shown that the thiol-ene-isocyanate UV-heat dual-curing TPU with different properties can be designed by controlling the monomers.According to the mechanical and optical properties of TPU,the structure and dosage of photoinitiator,the monomer structure of ene,the stabilization time at 30℃ and the molar ratio of SH/NCO were studied,and the optimum conditions of UV-heat dual-curing were determined.