Study And Application Of Photoinitiated Multiphase Radical Polymerization Of Polymerized Carbon Nitride/organic Borate

Compared with homogeneous photopolymerization,photoinitiator for multiphase photopolymerization can maintain photoactivity and can be recycled to avoid embedding into the reaction system,and overcome the problems of irritating odor,toxicity and migration usually encountered by small molecule photoinitiator,which meets the requirements of green chemistry.Semiconductor nanoparticles can collect photons and start the charge separation process,which is the reason why they can be used as multiphase photocatalysts to catalyze multiphase photopolymerization reactions.Polymeric carbon nitride(CN)is one of the most stable carbon and nitrogen compounds among many semiconductor nanoparticles,and has many advantages,such as good stability,suitable energy band,non-toxicity,good biocompatibility,etc.Therefore,the use of CN in multiphase photopolymerization has certain advantages.CN needs to initiate polymerization reaction together with coinitiator.As a coinitiator,common amine compounds in reports will cause problems such as yellow aging of products,which will affect product quality.Based on this,in this paper,TBABTB is selected as a coinitiator,and its anionic and cationic parts can produce reactive radicals to initiate polymerization of monomers and avoid problems such as product yellow and metal residue.The combination of CN and TBABTB provides a new idea for multiphase photoinitiation system and expands the application field of CN and TBABTB.The main research contents are as follows:(1)Study on photoinitiated polymerization of CN/TBABTBMesoporous CN was prepared by thermal polymerization of "Earth-abundant" urea,and formed a multiphase photoinitiator system with coinitiator TBABTB for free radical polymerization.At the same time,methyl methacrylate(MMA),the most typical monomer for free radical polymerization,was selected.Under the light condition of 365 nm UV lamp(10 mW·cm-2)at room temperature,The photopolymerization reaction is carried out in a quartz optical reactor,the effects of solid content,CN addition amount,TBABTB addition,solvent and reaction time on the polymerization reaction were systematically studied.The numberaverage molecular weight(Mn)and polydispersity index(PDI)of the polymerized products were tested by gel permeation chromatography(GPC)to explore the influence of photopolymerization conditions on the polymerization rate,Mn and PDI of the polymerized products.The results show that the polymerization rate increases with the increase of solid content,CN addition,TBABTB addition and solvent polarity.The relative molecular mass(Mn)of the polymerized products increased with the increase of solid content and decreased with the increase of TB ABTB addition,which was almost independent of the amount of CN addition and solvent polarity.The photopolymerization cycle experiment showed that the monomer conversion rate of CN reused for the eighth time could still maintain the activity at about 90%,which proved that CN still maintained high activity after separation and recovery.(2)Study on the photoinitiated polymerization mechanism of CN/TBABTB.Different comparative experiments were set up,and the results showed that the two components of CN/TBABTB photoinitiation system were indispensable for the occurrence of polymerization reaction,and it was proved that the tet-butyl ammonium positive ion and CN had a common photoinitiation effect.The photocontrol switch experiment proved that the CN/TBABTB reaction system was a photocontrollable reaction.Kinetic experiments show that the reaction time is proportional to ln([M]0/[M]),which proves that the CN/TBABTB photoinitiation system is a first-order kinetic reaction.Electron paramagnetic resonance(EPR)tests of CN/TBABTB and CN/TBAC systems have shown that both anions and cations of TBABTB can produce alkyl radicals.According to the experiment and test results of this paper,it is speculated that the reaction mechanism of this system is as follows:the photogenerated hole of CN acts on the boron anion part of TB ABTB to produce n-butyl free radicals,and the photogenerated electron acts on the tetrabutyl ammonium positive ion part of TB ABTB to also produce n-butyl free radicals to initiate monomer MMA polymerization.(3)Application research of CN/TBABTB photoinitiation systemThe system was used for the synthesis of photoresist film resin and composite hydrogel.The synthetic film forming resin and photogenic acid producing agent(HG-108)were prepared as chemical amplifying photoresist,after spin coating,pre-drying,exposure,post-drying,development of clear patterns,the best resolution can reach 6 μm.Using CN/TBABTB as a photoinitiator,the composite hydrogel obtained by light curing has stronger mechanical properties than the control hydrogel obtained by curing potassium persulfate/hydrogen peroxide system.