Synthesis And Cyclization Of Telechelic Polymer

Since the discovering of cyclic macromolecule of DNA, the synthesis of cyclic macromolecule has been one of the interested researches and the focus of scientific workers in the polymer science in the last several decades due to their unique character. Compared to linear, star or branche polymers, the cyclic polymers have been aroused a lot of widespread interest due to their many special theoretical characters such as the absence of end groups and the chemical and physical equivalence of chain structure. The current preparing methods of cyclic polymer are the intramolecular cyclization of the telechelic polymer in dilute solution. As a result of the existence of competition of chain-extension, the linear polymers are prepared simultaneously and are separated through post production, it is difficult to guarantee the high yield of the cyclic polymers. The theoretical and properly studies have been hindered by the limited sample, quantity and preparation. Therefore, the research of cyclic polymers prepared by new methods is a very challenging research topic with important theoretical and practical significance.In this paper, the cyclic polymers are prepared with modern synthetic technique on the basis of previous studies. First, theα-carboxyl-ω-chloro-linear polystyrene and poly(methyl methacrylate) with narrow molecular weight distribution and terminal functional groups were prepared by ATRP(Atom Transfer Radical Polymerization) using p-(chloromethyl)benzoic acid as initiator, then the cyclic polymers were synthesized through the coupling of both ends with potassium carbonate as catalyst under the highly diluted concentration. The method simplifies the steps and increases the yield of cyclic polymer.Nitroxide-Mediated―Living‖Free Radical Polymerizations (TEMPO) is a living/controlled free radical polymerization developed recently. Theα-carboxyl-ω-hydroxy linear polystyrene were prepared by TEMPO free radical polymerization using 4,4'-Azobis(4-cyanovaleric) acid as initiator and 4-hydroxy -TEMPO as free radical capturer. The cyclic polystyrene had been prepa- red using 2-chloro-1-methyl-iodopyridine/triethylamine as catalyst via intramolecular cyclization under the highly diluted concentration. The Cyclic PS-b-PCMS was prepared through the technique of the ring-expansion reaction. The amphiphilic novel cyclic polystyrene/polyacrylamide graft copolymer was prepared by ATRP using cyclic PS-b-PCMS as macro-initiator. Cyclic polymer can also synthesized by interface reaction taking advange of the highly dilute concentration of reactant at biphase interface which is required in cyclization. Through the interface reaction, the cyclic polystyrene had been prepared with high yield. First, two different linear polymers were synthesized by atom transfer radical polymerization and radical polymerization, respectively, then the cyclic polystyrene had been synthesized from the telechelic linear polymers with small water-soluble molecule at the interface between oil and water.The method reduces the possibility of extending chain reaction, and improves the cyclization field.