Synthesis And Characterization Of Cyclic Polymers With Complex Architectures

The development of living radical polymerization(LRP)and the emergence of new synthetic protocols have made it possible to synthesize various cyclic polymers with complex topology.Among the topological polymers,cyclic polymers have received much attention due to their unique"endless"structure.In this dissertation,a series of complex cyclic polymers were successfully synthesized by combination of LRP,UV-induced coupling reaction and self-accelerating click reactions.Moreover,by introducing dynamic chemical bonds,the transformation of the topology is achieved.The research results are summarized as follows:1.Multicyclic polymer with hyperbranched structure was successfully synthesized.A ATRP(Atom Transfer Radical Polymerization)initiator containing an alkynyl group protected by triisopropylsilane was synthesized which was used for ATRP of styrene.By combination of click reaction,UV-induced coupling reaction and post-modification,an AB2 type cyclic polystyrene containing both a protected alkynyl group and two azide groups was obtained,and after deprotection,the cyclic polymer was used as a macromonomer to produce multicyclic polymer with hyperbranched structure via AB2 strategy.Gel Permeation Chromatography(GPC)results showed that the obtained polymer had a high molecular weight compared to the cyclic macromonomer.2.Multicyclic polystyrene(PS)with hyperbranched structure was constructed in an efficient way by combination of ATRP,UV-induced cyclization and self-accelerating click reaction.Firstly,a seesaw type PS was synthesized via atom transfer radical polymerization(ATRP)using a Y-shape ATRP initiator containing one hydroxyl at center and bromine at each end.After azidation,the anthryl and hydroxyl groups were introduced to the ends of the polymer chain by click reaction with a trifunctional molecule bearing alkynyl,hydroxyl and anthryl groups(alkynyl-OH-ant).By irradiating with 365 nm UV light in a highly dilute condition,cyclic polymer with three hydroxyl groups(c-PS-(OH)3)can be obtained,then it was converted to a cyclic polymer containing three azides(c-PS-(N3)3)by bromination of the hydroxyl groups and azidation.This "A3" cyclic macromonomer was then used to construct hyperbranched multicyclic polymer via self-accelerating click reaction with sym-dibenzo-1,5-cyclooctadiene-3,7-diyne(DBA).The properties of obtained polymer were characterized by NMR,FT-IR,MALDI-TOF MS and TD-SEC.It was calculated from the MALLS results that there were about 35 "small rings" in the multicyclic polymer.Moreover,due to the photocleavage reaction of the anthracene dimer,this hyperbranched multicyclic PS can be cleaved to long-chain hyperbranched PS by irradiating with 254 nm UV light.3.A simple and efficient method to construct hyperbranched multicyclic polymer was introduced.First,a tailored trithiocarbonate with an azide group and an anthryl group at both ends,and an azide group in the middle was successfully synthesized,and this multifunctional trithiocarbonate was used as chain transfer agent(CTA)to afford anthracene-telechelic polystyrene(PS)via reversible addition-fragmentation chain transfer(RAFT)polymerization.After that,linear PS was irradiated under 365 nm UV light to achieve the cyclization process.The monocyclic polymer further reacted with DBA via "A2+B3" strategy based on self-accelerating click reaction to produce hyperbranched multicyclic polymer.The structures and properties of the polymers were characterized by NMR,GPC,UV-Vis spectrophotometry and TD-SEC.The resultant hyperbranched multicyclic polymer contained about 21 monocyclic units based on MALLS measurements.The plot of intrinsic viscosity versus molecular weight revealed that the a value of the unique hyperbranched multicyclic polymer was lower than both hyperbranched polymers and cyclic polymers.4.The cyclic polystyrene containing two hydroxyl groups was successfully synthesized by combining ATRP and UV-induced ring closure,then the ATRP initiator was introduced through the esterification reaction of hydroxyl group,followed by ATRP of styrene to obtain twin-tail-tadpole-shaped polymer.After azidation,the figure-8 shaped dicyclic polymer can be obtained by self-accelerating click reaction of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne at very low concentration.On the other hand,at high concentration,the twin-tail-tadpole-shaped polymer tends to react intermolecularly to form a"cyclic-liner-cyclic"multicyclic polymer.The GPC results showed that the multicyclic polymer contained 12 cyclic units averagely.In this way,we realized the synthesis of different topological polymers by simple concentration control.