Study On Organic Photo-redox Radical Polymerization Initiated By Arylsulfonyl Halides

It is well-known that the method of controlled/living radical polymerization has the robust ability in the precise synthesis of macromolecules,as well as the control of function of polymeric materials.In recent years,with the in-depth study in photochemical systems,photo-controlled radical polymerization especially photoredox catalysis systems with the advantages of low energy consumption,mildness,high efficiency and wide range of application has shown superiority in synthesis and modification of materials,which could not be achieved by other traditional methods.In addition,aromatic sulfonyl halides have been proven to be used as initiators in traditional thermo-initiated living radical polymerization and easily obtained from varieties of aromatic compounds.Therefore,the combination of visible light-driven,non-metallic catalysis and living radical polymerization initiated by aromatic sulfonyl halides would provide greater space of applications and development in preparation of polymers with precise structure,controllable molecular weight and molecular weight distribution.In this paper,a novel method of organic photoredox polymerization was established,which was carried out by using new catalyst of N-arylphenothiazine synthesized by own and a variety of aromatic sulfonyl halides as initiators under irradiation with visible light(white or purple LED lights source).In this work,three catalysts of N-substituted phenothiazine derivatives with visible light absorption were synthesized and characterized by cylic voltammetry(CV),ultraviolet spectroscopy and fluorescence spectroscopy.Excellent reduction ability of excited state and fluorescence quantum yields were found,especially 10-([1,1'-biphenyl]-4-yl)-3,7-bis(4-butylphenyl)-10H-phenothiazine(PC4)with N-biphenyl substituted has a fluorescence quantum yield of 61%.Those photoredox catalysts were used for the polymerization of methyl acrylate(MA)initiated by 4-methylbenzenesulfonyl chloride under irradiation from a white LED blub.Compared with other catalysts,PC4 used in polymerization has provided products with better control of molecular weight and narrow molecular weight dispersity.This system with a wide scope of(hetero)aromatic sulfonyl chloride initiators can be used to polymerize(methyl)acrylate or(methyl)acrylamide and provide polymers with controllable molecular weight and molecular weight dispersity between 1.21 ~ 1.73 by adding sodium bromide.Using MA as a template,the “living” feature of the polymerization method was demonstrated by chain extension experiments and end group analysis with MALDI-TOF and NMR,as well as repeatedly light “On/Off” experiments to prove the reliability of light control.Based on the method established in this paper,polymer brushes with different degrees of grafting were synthesized from polystyrene with different substitution densities as macro-initiators,which laid the foundation for the application of this type of polymer.