Study On The Novel Synthetic Method Of Aromatic Azoxy Compounds And Azoxy-Containing Polymers

Aromatic azoxy compounds,similar to aromatic azo compounds in structure and properties,have trans and cis isomers that can be reversibly transformed each other under the irradiation of light or heating,which have potential applications in optical materials.Additionally,as significant intermediates in organic synthesis,they can be reduced to azo and amine or catalyzed to some new compounds.In comparison with small molecules,polymers show good mechanical property and processability,providing wider potential applications in optical materials.In this thesis,we have developed an efficient and metal-free synthetic method for directly reducing nitroarenes to azoxyarenes.This efficient strategy was further employed to synthesize linear and hyperbranched aromatic azoxy-containing polymers as well as to sidechain aromatic azoxy-functionalized polymers by post-polymerization modification.The detailed results were summarized as following:（1）A novel and efficient approach for the synthesis of aromatic azoxy compounds using ultraviolet/visible light irradiation under mild conditions was developed.Initially,1a（2-nitro-9,9-dioctyl-9-H-fluorene）was used as a model substrate to explore the optimal conditions for the reaction.The reaction process was monitored by ¹H NMR in suit.Subsequently,the substrate scope was investigated and the results showed that this method was suitable for substrates with large conjugated systems,while nitrobenzene and its derivatives were difficult to be reduced to azoxyarenes under the present conditions.The obtained compounds were characterized by ¹H NMR,¹³C NMR,MOLDI-TOF-MS and UVvis spectra.The photoisomerization behaviors of obtained aromatic azoxy compounds were investigated by UV-vis spectra.These results showed that the photoisomerization of azoxyarenes（2aa–2ee）could be driven only by visible light.（2）Based on the results of the photoreductive reaction,we developed an efficient approach for preparing linear main-chain and hyperbranched aromatic azoxy-containing polymers directly from bis/trinitroarenes with high monomer conversion.The photoisomerization behaviours of the obtained polymers driven by visible light was further investigated.First,the bis/trinitroarenes monomers were synthesized.Then,the two monomers were polymerized respectively via photoreductive reaction.The mononitro compound,2-nitro-9,9-dioctyl-9-H-fluorene,was added to the polymerization system of trinitro-functionalized monomer as end-capping reagent to control the molecular weight and improve the solubility of hyperbranched polymer.The obtained linear main-chain and hyperbranched polymers were characterized by ¹H NMR,GPC,FT-IR and UV-vis spectra.The reversible photoisomerization of linear main-chain and hyperbranched polyamers were both investigated in THF,which presented good stability and fatigue resistance.（3）A novel approach for preparing side-chain azoxy-containing polymer via postpolymerization modification based on the photoreductive reaction was developed.Two kinds of monomers were synthesized and one of them contained aromatic nitro-functional group.The two monomers were then copolymerized via ring opening methathesis polymerization（ROMP）.The obtained copolymer was used to react with NHT via photoreductive reaction to prepare side-chain azoxy-containing polymers.The side-chain azoxy-containing polymer was characterized by ¹H NMR,GPC,FT-IR and UV-vis spectra.Finally,the photoisomerization behavior of the copolymer was tested.