Preparation And Characterization Of Functional Silicone Elastomer Via Thiol-ene Click Reaction

Silicone elastomers exhibit lots of unique properties,such as biocompatibility,high and low temperature resistance and corrosion resistance.Silicone elastomers have been widely used in aerospace,electronic equipment,biomedicine and transporation and will not be lack in our lives.With the lack of coal petrochemical resources on the earth,the silicone rubberwill be a promising alternative in the furture.Because of the increasing use of organosilicon materials,the recycling problem has aroused people’s concern gradually.To recycle and prolong the life of silicone rubber,we produced self-healing and thermoplastic silicone elastomers by thiol-ene click chemistry.Our work are mainly introduced in two aspects as follows:1)Preparation of self-healing silicone elastomer based on hydrogen bonding supramolecular self-assemblyFirstly,silicone oil with high vinyl content was synthesized,and then grafted with cysteamine or mercaptopropionic on the side chain by thiol-ene click reactionto obtain amino or carboxyl modified polysiloxanes.Finally,self-healing silicone elastomer was prepared by mixing these two kinds of modified polysiloxanes with the molar ratio of 1:1,and crosslinked with trimethylolpropane three(3-mercapto propionic acid ester).The hydrogen bonding supramolecular self-assembly formed from the reaction of amino and carboxyl endowed the self-healing property and the chemical crosslinking gave better mechanical property.The silicone elastomer exhibit dielectric properties because of the introduction of polar groups.Thus,the self-healing efficiency can be characterized by two ways,the mechanical properties and the dielectric properties.By the way of mechanical properties,the self-healing efficiency increased with the increasing of amino or carboxyl contents when they had the same crosslinking degree.With the chemical crossliking degree increasing,the self-healing efficiency reduced because the molecular self-assembly were restricted.The consequence also showed that higher temperatures were beneficial to self-healing properties.The self-healing efficiency of the elastomer can reached 44%at room temperature.When the temperature was 80 ℃,the self-healing efficiency reached the highest value of 99%.However,the self-healing efficiency reduced when the temperature was higher than 100 ℃.By the maximum actuation strain method,the result was consistent with the mechanical property method,the highest self-healing efficiency of the elastomer reached the highest value of 99%at 80 ℃.In addition,the silicone rubber exhibited great dielectric properities.The highest maximum actuation strain can reach 15.61%at room temperature,and the highest dielectric constant can reach 3.6,which was far higher than the ordinary silicon rubber.When the chemical crosslinking degree of silicone elastomer was same,the dielectric constant would rise with the increasing of grafting rate.Compared with the unmodified vinyl silicone rubber,dielectric loss increased considerably after grafting.With the increase of the grafting rate,the dielectric loss increased accordingly.The eletric volume resistivity of modified vinyl silicone rubber presented decreasing trend with the increasing of grafting rate,but the values were more than 1012 Ω*cm.So the silicone elastomer is still insulated.The self-healing silicone elastomers with great dielectric properties was prepared successfully.2)Preparation of three-block thermoplastic elastomer based on click reactionFirstly,thiol-terminated hard segment prepolymer was synthesized by reacting 4,4’-thiodibenzenethiol with 1,3-diisopropenylbenzenevia thiol-ene click chemical reaction.Its structure was characterized by FT-IR and 1H-NMR.The results showed that the hard segment prepolymer was much purer than the commercials.The preparation method was convenient and high efficiency,and the hard segment prepolymer obtained met all the requirements of dispersion phase of TPE.Then,the hard segment prepolymer were reacted with vinyl-terminal silicone oil by thiol-ene click reaction to prepare three-block thermoplastic elastomer.The three-block thermoplastic elastomer were formed.