Synthesis, Characterization And Properties Of New Double-cycloaddition Copolymers

It was very significant in both theory foundation research and practical application forpreparation of novel polymer with transition metal as catalysts and existing method for thesynthesis of organic compounds. The transition metal-catalyzed diyne cycloadditioncopolymerization and alkyne double-cycloaddition copolymerization had demonstratedusefulness of the transition metalcatalyzed alkyne cycloaddition reaction as apolymer-forming elementary reaction. This paper was based on transition metal-catalyzedcycloaddition reactions as a polymer synthesis of fundamental reaction, and thecopolymerization was one-step construction of a copolymer repeat unit with a complexstructure. In this study, we had developed an efficient, chemo-, and stereoselectivenickel(0)-catalyzed terminal diyne and maleimide double-cycloaddition reaction which wasnew to afford polymers with rigid fence-like structure.Nickel(0)-catalyzed double-cycloaddition reactions of4,4’-diethynlbiphenyl,2,9-diethynlfluorene,1,7-octadiyne and1,4-bis(ethynyl)-2,5-dialkoxy-p-phenylene withN-n-octylmaleimide or N-phenylmaleimide to afford many new comb-like structure polymerswere investigated in THF. The influence of terminal diyne and maleimidedouble-cycloaddition reaction temperature and time was investigated, then the resultssuggested that double-cycloaddition yields decreased as reaction temperature rised, but theyincreased with the improvement of reaction time. The structures of double-cycloadditionpolymers were identified by IR and NMR. The composition of the copolymer was estimatedby1H NMR spectra integral area, and we discussed the mechanism of aromatic diyne andmaleimide double-cycloaddition. The results showed that copolymerization of1,4-bis(ethynyl)-2,5-dialkoxy-p-phenylene and N-phenylmaleimide was just single-cycloaddition.Finally, comprehensive examinations of polymers including thermal analysis, ultravioletabsorption spectrum analysis, fluorescence spectrum analysis and electrochemicalperformance analysis had been done.We found that major polymers were soluble in common organic solution (such as CHCl3,THF, CHCl2et.), part of polymers with high yields(about70%), high molecular weight(thehighest Mw is1.25×105), good thermostability(the temperature of5%weight loss is325℃). Fluorescence spectrum analysis showed that polymers emit purple-blue or blue light in CHCl2solution. Cyclic voltammetry discovered the HOMO of polymers was-6.2eV or lower.