| Thiol-ene click chemistry has an advantage of mild reaction condition,fast reaction rate,high yield,etc.Although photopolymerization technique is a rapid,energy-saving and environment friend technology,there are serious problems such as large volume shrinkage and oxygen hinder effect for traditional acrylate photopolymerization system,which can be solved by thiol-ene system.But due to large number of flexible thioether bond existing,it is often associated with the disadvantage of low glass transition temperature.In this study,the uses of one-step combination process of inorganic crosslinking network formed by siloxane group hydrolytic condensation and organic crosslinking network formed by thiol-ene click chemistry to not only improve the low glass transition temperature of traditional thiol-ene system,but also improve the mechanical properties by changing the reaction conditions and reactant species.The content and conclusions of the subject are as follows:the organic and inorganic hybrid networks were prepared with pentaerythritol tetrakis(3-mercaptopropionate)/triglycoldimercaptan,1,3,5-triallyl-1,3,5-tria-zine-2,4,6(1H,3H,5H)-trione/poly(ethylene glycol)diacrylate and 3-(trimethoxysilyl)-1-propanethiol as monomers,4-(octyloxy)phenyl]phe-nyl-iodonium as photo-acid generator,TBDˇ`HBPh4 as photo-base generator,and isopropyl thioxanthone(ITX)as a sensitizer.Thiol-ene click reaction,and hydrolyzation and condensation of siloxane group were catalyzed by photo-base and photo-acid.Several different hybrid system were studied with adding inert resin and changing the degree of polyfunctional types of mercaptan,alkene monomers.The influence of compositions of the hybrid systems on the polymerization kinetics,the thermal stability,mechanical properties,hardness,solvent resistance and surface microstructures were investigated.The results showed that:1.The photo-acid and photo-base can catalyze thiol-ene system to achieve homogeneous organic/inorganic hybrid crosslinking network indeed.2.The mechanism of photo-acid catalyzed system is radical polymerization,and that of photo-base system is radical polymerization and anionic polymerization.3.According to the polymerization kinetics result,both the reaction rate of thiol-ene and hydrolysis of the siloxane group for photo-acid system are faster than that of the photo-base system.However,the scanning electron microscope experimental results showed that photo-base system exhibited higher condense reaction conversion of silanol group than photo-acid system and showed better homogeneity for hybrid network.4.The comprehensive mechanical properties of the photo-acid system could be improved by reducing the density of thiol/ene,and that for photo-base system could be enhanced by adding the inert resin,which are both due to decreasing of the crosslinking density of the hybrid network. |
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