Construction Of Supramolecular Polymers Based On Double Host-guest Recognition Of Crown Ethers And Pillararenes With Triplet Pyridine Metal Coordination

Supramolecular polymer is the integration of polymer science and supramolecular chemistry,supramolecular polymers are reversible polymer arrays assembled by monomer units through weak non-covalent interactions.Compared with the single macrocyclic host-guest recognition,the dual host-guest recognitions of crown ethers and pillararenes will synergistically enrich the structures and function of supramolecular polymers with unique physical and chemical properties.On the other hand,the metal coordination were also widely applied to constructed various supramolecular structures because of its good directionality and strength.In this dissertation,we reported the orthogonal molecular recognitions between crown ethers and pillararnes-based host-guest interactions and complemental metal coordination interactions.New supramolecular polymer were construted based on these supramolecular forces and their stimulus responsiveness were also studied.The details are as follows:（1）Two novel supramolecular polymers were controllably constructed by hierarchical self-assembly and the structural transformation were realized.Firstly,three monomers A₂B₂,C_2,and D₂ with different structures were designed and synthesized.The monomer A₂B₂ consists of two crown ether groups（B21C7）and two neutral guest groups（TPN）.The monomer C₂ is composed of two secondary ammonium salt groups（TAS）;The monomer D₂ is composed of two pillar[5]arene groups（P5）bridged by a boron-dipyrrole methylene group（BODIPY）.A₂B₂+C₂ can form supramolecular linear polymer（SLP）through the host-guest reaction of crown ether and secondary ammonium salt in solution.After D₂ was added to SLP solution,the SLP was transformed into a higher molecular weight supramolecular crosslinked polymer（SCP）due to the complexation of the pillar[5]arene and the neutral guest.In dilute solution,the fluorescence of SCP was enhanced compared with D₂.When the concentration of monomer A₂B₂ exceeds 85 m M,the supramolecular crosslinked polymer changed into a supramolecular gel and emitted green fluorescence.The reversible phase transition of gel-sol can be realized by adding/removing K⁺or heating/cooling the gel,accompanied by the decrease or enhancement of fluorescence emission intensity.（2）A new supramolecular crosslinked polymer（SCP）was constructed based on the complementary metal coordination.Firstly,two monomers M1 and M2 with different structures were designed and synthesized.M1 monomer is composed of two tripyridine derivatives tey（6,6"-anthracyl tripyridine of tpy）bridged by a tetraethylene group（TPE）;M2 monomer is composed of three tripyridine（tpy）groups.After M1,M2 and Zn（OTf）₂ were dissolved in the mixed solution of chloroform and acetonitrile（1:2,v/v）,a SCP was constructed by the self-assembly of M1+M2+Zn（OTf）₂ through the complementary metal coordination of tpy-Zn²⁺-tey.The fluorescence intensity decreased with the increase of Zn（OTf）₂ compared to the free uncoordinated M1+M2.Adding alkali/acid to the SCP can reversibly induce the fluorescence emission enhancement or decay,which shows that acid and alkali can control the fluorescence switch of SCP.Furthermore,when the concentration of SCP exceeds 30 m M,the supramolecular gel will be formed.The supramolecular gel can realize the reversible phase transition of gel-sol by heating or cooling.