Nitroxide Polymer Brushes Prepared By Surface-initiated ARGET ATRP And Their Applications

TEMPO(2,2,6,6-tetramethyl-piperidine-1-oxyl)and its derivatives are very stable free radicals,they are dramatic and have a lot of potential applications.TEMPO as catalyst used in the process of selective catalytic oxidation of alcohols,shows mild reaction conditions.It has excellent properties such as high selectivity and high active.On the other hand,it has small toxicity,and can be used as an efficient inhibitor.But the price of TEMPO is too high and it is difficult to recover after the reaction,this is the technology bottleneck of the wide applications of TEMPO.The TEMPO loading on the carriers,and achieve the cycle using,is an important research field.With polystyrene(PS)microspheres as the matrix and methyl methacrylate(MMA),glycidyl methacrylate(GMA)and 2,2,6,6-tetramethyl-4-piperidyl methacrylate(TMPM)as monomers,three PTMPM polymer brushes,with different chains including homopolymer brushes(PS-PTMA,PS-PGMA and PS-PTMPM),block copolymer brushes(PS-P(MMA-b-TMPM)and PS-P(MMA-b-GMA))and random copolymer brushes(PS-P(MMA-co-TMA))were synthesized via surface-initiated ARGET(activators regenerated by electron transfer)ATRP(atom transfer radical polymerization).Then the polymer brushes with TEMPO units were obtained by two methods of oxidation and ring-opening reaction.Oxidation was to oxidize the TMPM units using3-chloro benzoic acid peroxide(m CPBA)to yield nitroxide radical units.With this method we obtained the homopolymer brushes PS-PTMA,block copolymer brushes PS-P(MMA-b-TMA)and random copolymer brush PS-P(MMA-co-TMA).Furthermore,the ring-opening reaction between the large number of epoxy groups in the polymer brush(PS-PGMA,PS-P(MMA-b-GMA))and the hydroxyl groups in 4-OH-TEMPO was carried out,consequently obtaining nitroxide polymer brushes of homopolymer brush PS-PGMA-TEMPO and block copolymer brush PS-P(MMA-b-GMA-TEMPO).Finally the oxidized nitroxide polymer brush was used as a catalyst in the selective catalytic oxidation of alcohol.The catalytic property and mechanism of the products,polymer chains and polymer brushes,were studied in the two systems of selective catalytic oxidation of alcohols.The study found that nitroxide polymer brushes had outstanding properties,such as significantly higher catalytic performance and easy recyclability,compared with nitroxide polymer chains.The nitroxide polymer brushobtained by ring-opening reaction as a supported inhibitor was successfully applied in the synthesis of epoxidized soybean oil acrylate(AESO),showing a good inhibiting effect and easy recyclability.Then the supported TEMPO inhibitor(nitroxide polymer brush)and free TEMPO inhibitor(4-OH-TEMPO)were combined as a compound-inhibiting system to synthesize AESO.After synthesis,the supported inhibitor was recovered by filtration and the free inhibitor was reserved in AESO to prevent it from gelling in the storage process.AESO with excellent performance and low inhibitor residual was obtained through use of this combined inhibitor.Thus,the compound inhibitor can meet the different inhibitor needs for the synthesis and storage processes.The recycling performances of both brushes were good.The results showed that the esterification rate did not fall significantly after six cycles.