The Exploration Of Supported Click Polymerization Catalysts

Cu（Ⅰ）-catalyzed azide-alkyne cycloaddition "click" reaction possesses such advantages as mild reaction conditions, high efficiency and yields, regioselectivity, functionality tolerance, wide range of applications, as well as simple product isolation. It has been widely used in the preparation of nanomaterials, drugs and bioconjugates, surface modification and post-functionalization of polymers.The polymer synthesis chemists have nursed the efficient click reaction into a new polymerization method, i. e. click polymerization. However, for the metal complex catalyzed click polymerization, the removal of the catalytic residues from the resulting polytriazoles is difficult. The catalyst residues will cause cytotoxicity and deteriorate photoelectric properties of the polymers, which greatly limits the application of the click polymerization in biomedical and photoelectric fields.To solve the problem of metal residue in the polymerization products, we have developed three kinds of metal-free click polymerization. However, these polymerizations are lack of monomers, require high reaction temperature. Thus, it is crucial to find another way to reduce the metal residues in the resulting polymers.This thesis establishes a new azide-alkyne click polymerization （AACP） route with supported catalysts, through which the copper residue of the product is greatly decreased and the catalysts are recyclable and reusable.Firstly, through the coordination of CuI to the dimethylaminomethyl-grafted Amberlyst^? A-21 resin, we prepared the first kind of supported Cu（Ⅰ） catalyst. The CuI@A-21 could catalyze the AACP of different diazides and dialkynes in THF at 60 ℃ for 12 h, producing 1,4-regioselective polytriazoles with high yields, high molecular weight, narrow polydispersity and low copper residue content. It is also very stable and could be reused for 4 cycles. More importantly, the polytriazoles prepared by CuI@A-21 possesses a higher fluorescence efficiency than that catalyzed by traditional Cu（PPh3）3Br.Secondly, the phenanthroline modified supported catalyst CuI@PS-Phen was desighed and prepared, which can efficiently catalyze the AACP to produce soluble polytriazoles with high molecular weights （Mw>30800）, and low copper residue content （<410 ppm） in high yields （up to 94.2%） under mild reaction conditions without the exclusion of oxygen. It greatly simplifies the procedures of AACP, and further meets the definition of click chemistry that the reaction condition should be mild.Finally, through the comparison of different kinds of the ligands and carriers, we found that polystyrene resin was the best catalyst support. The porous structure of the PS resin endows it with large specific surface area which results in better catalytic performance. Furthermore, the variety of PS resins makes it easy to be modified and prepared. The copper residue content in the polymerization products could be reduced by the ligands with high coordination ability. But those ligands, such as TBTA and cyclen, may result in poor catalytic performance because they will restrict the formation of the coordinated intermediate. It is a dynamic balance of the Cu（I） catalyst amongst the supports, solvents, alkyne monomers and the triazole rings in the products.