Design,Synthesis And Properties Of Cationic Photopolymerizable Fluorosilicone Monomers

Fluorosiloxane polymers combine the advantages of organic silicon and organic fluorine and exhibit outstanding thermal stability,corrosion resistance,hydrophobicity and lipophobicity,and thus they have been widely concerned in various fields.In recent years,because of the rapid development of UV curing technology,people focus on energy-saving green photopolymerization technology instead of time-consuming and energy-consuming heat-induced polymerization.Photocurable fluorosilicone monomers and polymers are attracting increased attention in the engineering fields.At present,most of the studies on photocurable fluorosilicone monomers focus on fluorosilicone monomers and polymers used for free radical photopolymerization,mainly fluorosilicone（methyl）acrylate monomers and polymers.However,being different from free radical photopolymerization,cationic photopolymerization has no oxygen inhibition and small volume shrinkage.In addition,epoxy monomers are favored by people for their low irritation to the human body and excellent mechanical properties.However,the high cost and complex synthesis procedure required for the preparation of fluorosilicone monomers and polymers hinder their wide application,and therefore how to prepare excellent fluorosilicone monomers and polymers by low-cost and simple synthesis process is an urgent problem to be solved.Based on this,in this work,three kinds of hydrogen-containing silicone oil with trifluoromethyl（FSi_nH）were synthesized by anion ring-opening polymerization of trifluoropropyl methyl cyclotrisiloxane and chlorodimethylsilane,and then glycidyl ether group,epoxy group and oxetane group,respectively as photosensitive groups were introduced to obtain three types of fluorosilicone monomers（GE-FSi_n,CE-FSi_nand XE-FSi_n）including nine monomers.Their synthesis steps were few and the process was simple.In addition,the short fluorine chains contained in them are of low biohazard and can bring low surface tension.The synthesized cationic photopolymerable fluorosilicone monomers were mixed with the commonly used commercial epoxy monomers,3,4-epoxy-cyclohexyl methyl 3,4-epoxy-cyclohexyl formate（E4221）and1,2-epoxy-4-vinylcyclohexane（VOH）,to prepare the photo-curing material with excellent hydrophobicity,toughness,tensile property and heat resistance.This work can enrich the research idea of cationic photopolymerization fluorosilicone monomers and provide a new feasible strategy to solve the problem of their high application cost.The main research contents and conclusions are as follows:1.Three kinds of trifluoromethyl silicone glycidyl ether epoxy monomers（GE-FSi_n,n=3,6,9）,trifluoromethyl silicone epoxy monomers（CE-FSi_n,n=3,6,9）and trifluoromethyl silicone oxetane monomers（XE-FSi_n,n=3,6,9）were successfully synthesized.2.Compared with E4221/VOH blank control system,the final epoxy conversions of the photocuring systems with GE-FSi_nare increased,and the properties of the material including water resistance,heat resistance and tensile properties are improved,but the hardness is reduced.When the addition amount of GE-FSi₆was 0.5 mol%,the material had the best comprehensive performances,the water angle was increased to 107.2°,glass transition temperature（T_g）was 160.1 ℃.T_5%,T_max1and T_max2reached 162 ℃,270 ℃ and 403 ℃,respectively.The pencil hardness of the cured film was B,and the adhesion on iron sheet and glass reached the highest level 0.Adhesion to PVC substrate remained at level 3.The elongation at break was 44.76%that was about twice as much as that of the blank control system,and the tensile strength is 0.4 MPa.3.Compared with E4221/VOH blank control system,the final epoxy conversions of the photocuring system with CE-FSi_nare increased,and the properties of the material involving water resistance,heat resistance and tensile properties are boosted,but the hardness is reduced.When the addition amount of CE-FSi₆was 0.5 mol%,the material had the best comprehensive performances,the water angle was increased to 104.1°,T_gwas 157.6 ℃.T_5%,T_max1and T_max2reached 177 ℃,270 ℃ and 403 ℃,respectively.The pencil hardness of the cured film was B,and the adhesion on iron sheet and glass reached the highest level 0,while the adhesion to PVC substrate remained at level 3.The elongation at break was 60.22%that was about three times as much as that of the blank control system,and the tensile strength was 0.35MPa.4.Compared with E4221/VOH blank control system,the final epoxy conversions of the photocuring system with XE-FSi_nare increased,and the properties of the materials including water resistance,heat resistance and tensile properties are enhanced,but the hardness is reduced.When the addition amount of XE-FSi₆was 0.5 mol%,the material had the best comprehensive performances,the water angle was increased to 108.4°,T_gwas 160.8 ℃.T_5%,T_max1and T_max1reached 171 ℃,252 ℃ and 403 ℃,respectively.The hardness of the cured film was B,and the adhesion on iron sheet and glass reached the highest level 0.Adhesion to PVC substrate remains at Level 3.The elongation at break is 69.92%that was more than three times that of the blank control system,and the tensile strength is 0.45 MPa.