Study On Host-guest Complex,Supramolecular Polymers And LCST In Crown Ether System

Many materials in nature have noncovalent interactions.These noncovalent interactions make some materials have dynamic and reversible properties.Inspired by natural substances,researchers have developed a variety of synthetic compounds with stimulus response characteristics.For example,using host-guest interaction to construct molecular recognition system;Using hydrogen bonds to design adhesives with advanced functions such as stimulus responsiveness,on-demand bonding and debonding capabilities,surface selectivity or recyclability;Using noncovalent interactions to construct a supramolecular system with thermal responsiveness.Hydrogen bond and host-guest interaction are two important noncovalent interactions in supramolecular systems.For example,supramolecular compounds can complex with metal ions or organic salts,which may be able to form supramolecular polymers.This kind of complex structure can also be introduced into polymer compounds,leading to the appearance of special functions.Another noncovalent interaction,hydrogen bond,is a ubiquitous force in nature.For supramolecular compounds,the reversibility of hydrogen bond brings stimulation response to materials,such as the changes caused by temperature,acid or base.LCST is one of the examples that some supramolecular compounds have in water.In the first part,we designed and synthesized two compounds with similar structures,one is K~+-benzo-21-crown-7 complex,and the other is the same crown ether without complexing K~+.By introducing coumarin unit into benzo-21-crown-7structure,we can easily obtain its single crystal and fluorescent emission.Then we further studied the changes of the basic properties of the host-guest pairs induced by K~+,including solubility,crystal structure,NMR spectra and fluorescence emission behavior during molecular recognition.Because of the typical host-guest interaction between the secondary ammonium salt and benzo-21-crown-7,we use the secondary ammonium salt as a comparison.We found that comparing their solubility is a simple way to judge whether the crown ether is complexed with K~+.In the second part,we also designed and synthesized two compounds with similar structures,both of which are benzo-21-crown-7-functionalized esters.The central structure of one compound is pentaerythritol,and the other is pentaerythritol ethoxide.The former have relatively strong viscosity,and the composition of this supramolecular compound is special.Different from many supramolecular polymers,it does not need to add solvent to polymerize.It could combine with water in the environment to form the supramolecular compound.The viscosity of this supramolecular compound is reversible because it is driven by noncovalent interaction,so it is helpful for recycling of substrate materials they adhere to.In the third part,we found that the compounds synthesized in the second part have not only viscosity but also LCST.Therefore,we designed and synthesized another compound as a compare.This compound is also a benzo-21-crown-7-functionalized ester.The difference is that its central part of the structure is composed of ethylene glycol.We found that this compound also has LCST.