Study On The Regulation Of LCST Behavior In Crown Ether System

In recent years,as smart appliances,smart devices,and intelligent medical treatment enter people's vision,smart materials have become an increasingly important part of people's production and life.The so-called smart materials are new functional materials that are perceptible and responsive to external shocks,and capable of self-monitoring,self-judgment and self-processing.As a part of smart materials,thermal responsive materials have been made many explorations on their mechanism of action and application development by scholar.Low critical phase transition temperature(LCST)materials are the most widely studied class of thermally responsive materials.However,the research on the behavior of LCST is concentrated in polymer field currently,rarely involving small molecule systems,and the scope of research is also limited relatively.Crown ether,as the first generation host molecule of supramolecular chemistry,is widely used in thermal response systems because of its amphiphilic nature.Therefore,in this thesis,starting from a small molecule system,with crown ether as the main body,the LCST behavior is regulated by introducing cationic selectivity,degradability and hydrogen bonding properties of water molecules.This thesis is mainly composed of the following three partsIn the first part,we designed and synthesized four tri-crown ether compounds with different ring sizes.Due to the hydrophilicity of the ethylene glycol chain,the larger the crown ether ring,the better the water solubility.We found that the smaller crown ether compounds have the lower T_cloudat the same concentration through UV-Vis spectroscopy.And we don't found that the compounds with the smallest crown ether ring has the LCST phenomenon.We further regulate the LCST behavior of crown ether compounds and their T_cloudby size-matching selectivity with cations.In the second part,pentaerythritol derivatives with four crown ether units were prepared by the conjugate reaction of acid chloride compound and crown ether units.This pentaerythritol derivative not only has the traditional LCST behavior,but also has a time-dependent LCST phenomenon.We have determined the degradability of pentaerythritol derivatives in water by nuclear magnetic resonance,discrete fourier transform,dynamic light scattering and diffusion ordered spectroscopy,and proposed a may degradation mechanism for the intramolecular cyclization process.In the last part,we designed and synthesized two similar crown ether compound one with aldehyde group and the other without aldehyde group.In comparison,the solubility of the crown ether compounds containing aldehyde groups in ethanol is more affected by water molecules.We found that only the compounds containing aldehyde groups have LCST phenomenon in aqueous solutions.We verified the hydrogen bonding between water molecules and aldehyde groups by single crystal diffraction,fluorescence,infrared spectroscopy and discrete fourier transform.We used hydrogen bonding to separate these two analogs simply and efficiently,which provides a new idea for the separation and purification of analogs.