Synthesis And Application Of Polystyrene-based Dual-functional Polymer Brushes

Polymer brushes had important applications in many fields due to their outstanding characteristics in adsorption,adhesion,lubrication and wetting.By loading the nitrogen-oxygen radical and sulfonic acid onto the polymer brush,the dual-functional polymer brush could be prepared,which had the potential application in the fields of catalysis and inhibition.This method could solve the problem that the free nitrogen-oxygen radical and sulfonic acid were difficult to recycle.In this paper,two chloride polystyrene spheres were selected as carriers to prepared polymer brushes containing nitrogen-oxygen radicals and sulfonic acids by surface grafting.These burshes were applied to the selective catalytic oxidation of alcohols,the synthesis of N-(ethoxymethyl)aniline and the synthesis of methoxypolyethylene glycol methacrylate(MPEGMA).The catalytic and inhibiting-polymerization characteristics were studied.Firstly,using methacrylate 2,2,6,6-tetramethyl-4-piperidyl ester(TMPM)and styrene(St)as monomers and micron chloromethylated cross-linked polystyrene microspheres as macromolecular initiator,PS-PSt-PTMPM,a block copolymer brush containing TMPM chain segment and St chain segment,was synthesized by the electron transfer activation regeneration catalyst atomic transfer radical polymerization(ARGET ATRP).Then the piperidine groups of TMPM were oxidized by 3-chloroperoxybenzoic acid to nitrogen-oxygen free radicals,and finally St units were sulfonated by sulfuric acid to obtain PS-PSH-PTMA,a micron-level dual-functional polymer brush loaded with nitrogen-oxygen free radicals and sulfonic acids.The dual-functional polymer brushes were characterized by FTIR,SEM,EDS,GPC,ESR and titration.Then,to made the dual-functional polymer brush more recyclable,the PS matrix was replaced with magnetic PS spheres with core-shell structure(SG-Fe₃O₄@PS-Cl).Polymer brushes with different chain structures were prepared,including homopolymer brushes SG-Fe₃O₄@PS-PSH,SG-Fe₃O₄@PS-PTMA and block copolymer brushes SG-Fe₃O₄@PS-PSH-PTMA.The magnetic polymer brushes were characterized by FT-IR,TGA,TEM,ESR,laser particle size analyzer and chemical titration.Finally,PS-PSH-PTMA and SG-Fe₃O₄@PS-PSH-PTMA,which had both acid catalysis and free radical capture,were used as catalysts for selective catalytic oxidation of benzyl alcohol,which could reach over 97%of the catalytic level of TEMPO and had great recycling performance.As acid catalysts,they were used for the synthesis of N-(ethoxymethyl)anilin,the catalytic performances were better than that of p-toluene sulfonic acid and large-pore strong acid resin,and the recycling performance was excellent.It was used to prepare MPEGMA instead of small-molecule acid catalyst and inhibitor,and the results showed that the dual-functional polymer brush could not only play an effective role in inhibiting polymerization,but also have a good acid catalytic effect in the synthesis of MPEGMA.Compared with p-toluene sulfonic acid and macroporous strong acid resin,the reaction time was greatly reduced.The catalysts were recovered by filtration or magnetic field.The catalytic performance was good after 5 times of recycling and the esterification rate was more than 99%.