Supramolecular Polymers Constructed By Macrocyclic Host-guest Reactions And Metal Coordination

Supramolecular polymers,as a combination of supramolecular chemistry and polymer chemistry,have attracted extensive interest of supramolecular and polymer chemists in recent years.With the development of supramolecular science,a variety of supramolecular polymers with specific structures and functions have been prepared.The structure of supramolecular polymers mainly includes the supramolecular polymers composed of single non-covalent reaction and the supramolecular polymers driven by multiple non-covalent reactions.Compared with the supramolecular polymers constructed by single non-covalent reaction,the supramolecular polymers driven by multiple non-covalent reactions can not only endow the structural novelty to supramolecular polymers,but also give them a variety of new functions.The main research contents of this paper include:(1)New supramolecular polymers were fabricated based on orthogonal self-assembly and competitive self-sorting assembly.Firstly,three different monomers AB,AE and D₂ were synthesized.The AB contains a terpyridine(tpy)group and a crown ether group(B21C7);and the heteroditopic monomer AE bears a 9-anthracenyl substituted terpyridine group(tey)and an B21C7group;and the monomer D₂ contains two secondary amine salt groups(DAS)connected by an alkyl chain.When the monomers AB,D₂ and zinc ions(molar ratio:2:1:1)were mixed in solution,they can form a fluorescent supramolecular polymer SP1 through orthogonal self-assembly.In constrat,AE+D₂+Zn(OTf)₂ only form oligomers due to the steric hindrance of the anthracene group on AE.When AE was added to the solution of supramolecular polymer SP1,the supramolecular polymer SP1 was disassembled and transformed a new supramolecular polymer SP2 with AE based on the competitive self-sorting assembly.Adding alkali(TBAOH)or chelating agent(EDTA)can result in fluorescence quenching of polymer solutions or polymer-based devices due to the removal of the metal ions from the backbone of the supramolecular polymer SP1.In contrast,the fluorescence intensity of the supramolecular polymer SP2 increased by removing the metal ions.(2)New sequence-controllable supramolecular copolymers were constructed by self-sorting assembly of multiple non-covalent interactions.First,four monomers M1,M2,M3 and M4 were designed and synthesized.M1 consists of a terpyridine(tpy)group and a neutral guest;M2 has a 9-anthryl substituted terpyridine group(tey)and a crown ether group(B21C7);M3 contains two pillar[5]arene(P5)groups;M4 consists of two dialkylammonium salt moieties.At high concentrations,M1+M2+M3+M4+Zn(OTf)₂ can self-assemble into supramolecular copolymer by the pillar[5]arene-TAPN host-guest reaction,B21C7-secondary ammonium salt and tpy-Zn²⁺-tay metal coordination reaction.By means of nuclear magnetic resonance spectroscopy,UV-vis spectroscopy,viscosity measurement,dynamic light scattering,fluorescence spectroscopy and transmission electron microscopy experiments,the self-sorting assembly of the four monomers was studied.Experimental results show that supramolecular polymerization depends on the initial concentration of monomers.The obtained supramolecular copolymer(SCP)shows responsiveness to potassium ions and succinonitrile,and increasing potassium ions can drive the decomposition and reassembly of SCP.In addition,the addition of alkali(TBAOH)can also induce enhanced fluorescence emission of the SCP-based solution or film.