Synthesis Of Dendritic Polyisocyanides By Double-arm Palladium Complexes Catalysts

In recent years,the development of artificial helical polymers has made considerable progress,and many kinds of helical polymer materials with new functions have been developed.Helical polyisocyanides(PIs)have attracted a lot of attention due to the unique rigid rod helical structure.PIs with different topological structures such as polymer brushes and star polymers have been successfully prepared.However,the research on dendritic PIs has been rarely reported.Because dendritic polymers have a clear and regular structure,they have a wide range of applications and become one of the research hotspots.In this thesis,a new double-arm palladium complex catalyst was first designed and synthesized.One end of the catalyst has a hydroxyl group that can be esterified,and the initiator can be introduced into the polymer chain by transesterification with the end groups of the polymer.The other end has two Pd active polymerization sites,when the initiator is introduced into the end of the polymer chain,a branching site will be generated.The designed double-arm palladium complex could give the formation of a branched polymer with a clear structure in the isocyanides polymerization.In this thesis,the synthesized hydroxyl functionalized double-arm palladium complex as a catalyst to prepared a well-defined dendritic PIs by a new stepwise iterative method including isocyanides polymerization,the introduction of ester groups at the end groups,and transesterification of the end groups.Finally,a series of dendrimers up to the fourth generation(4G)were successfully synthesized.These polymers were characterized by NMR and FT-IR spectra.The molecular weight(M_n)of 4G dendrimers with the highest generation G4-P1-Pd and G4-P2-Pd is 49.4 and 66.5 k Da,respectively.The dendrimers also possess narrow molecular weight distributions.Herein a series of dendritic PIs with high molecular weight and narrow molecular weight distributions can be obtained by this method.