Fast Living Polymerization And Helix-sense-selective Polymerization Of Diazoacetates

In this work,air-stable palladium(?)catalysts bearing bidentate phosphine ligands were designed and prepared,which could initiate fast and living polymerizations of various diazoacetate monomers under mild conditions.The polymerization afforded desired polymers in high yields with controlled molecular weights(M_ns)and narrow molecular weight distributions(M_w/M_ns).The M_ns of the isolated polymers were linearly correlated to the initial feed ratios of monomer to catalyst,confirming living/controlled manner of the polymerizations.The M_n also increased linearly to the monomer conversion,and all the isolated polymers showed narrow M_w/M_ns.The polymerization was relatively fast,and can be accomplished within several minutes.Such fast living polymerization method can be applied to a wide range of diazoacetates monomers in various organic solvents at room temperature under air.Taking advantage of the living nature,a series of block copolymers were facilely prepared through chain extension reactions.The amphiphilic block copolymers synthesized by this method exhibited interesting self-assembly properties.Moreover,polymerization of achiral bulky diazoacetate by Pd(?)catalysts bearing chiral bidentate phosphine ligand lead to the formation of polydiazoacetates with high optical activity due to the formation of one-handed helix of the main chain.The helix-sense of the polymers was determined by the chirality of the Pd(?)catalysts.