Kinetic Study Of Dissipative Liquid-Liquid Phase Separation Assembly System By NMR

Molecular assembly is of great importance for generating new substances and providing new functions.Assemblies with special functions that cannot be obtained by conventional chemical synthesis have been prepared through assembly methods.At present,most of the artificial molecular assembly systems are under thermodynamic or kinetic equilibrium.In recent years,dissipative molecular assembly has gained intensive research attention,especially dissipative assembly systems driven by chemical reaction networks exhibiting unique structures and functions.The assembly process of important living systems usually proceed in the dissipative state.The liquidliquid phase separation phenomenon in cell is one of the important life processes in the dissipative state.The dissipative liquid-liquid phase separation process is closely related to the life process,and its mechanism research has important scientific and practical significance.However,the mechanistic study of the dissipative liquid-liquid phase separation system is challenging in both construction of the system and its in-situ and high-resolution characterization.This thesis focuses on dissipative molecular assembly,including designing and constructing artificial dissipative liquid-liquid phase separation assembly system,in-situ and high-resolution characterization using nuclear magnetic resonance,and revealing the physical-chemical mechanism of the dissipative liquid-liquid phase separation assembly system.The assembly system in this dissertation might provide model chemical systems for studing the liquid-liquid phase separation process of life systems.This thesis is divided into the following three parts:In the first part of the work,we successfully constructed the artificial dissipative liquid-liquid phase separation assembly system.Using carboxylic acid as the precursor and EDC as the fuel,we constructed a series of dissipative liquid-liquid phase separation assembly system based on anhydride bond,we also changed the structures and properties of precursors and added isotope markers(19F),such as 4cfluorophenylacetic acid.2,4,6-trifluorophenylacetic acid and 4-(trifluoromethyl)phenylacetic acid.The phase separation process could be characterized by 19F-NMR spectroscopy,which provided the feasibility for quantitative analysis of the kinetic process of phase separation by NMR.In the second part of the work,we investigated the kinetic processes of the dissipative liquid-liquid phase separation assembly system by 19F-NMR spectroscopy.The dissipative liquid-liquid phase separation assembly system was constructed using 4-fluorophenylacetic acid or 4-(trifluoromethyl)phenylacetic acid as precursor respectively and EDC as fuel.The kinetic processes at different temperatures were monitored.According to the NMR results,we drew the kinetic curves and established the kinetic model to systematically study the physical-chemical mechanism of the dissipative liquid-liquid phase separation assembly process.In the third part of the work,we conducted preliminary explorations on application of the dissipative liquid-liquid phase separation assembly system,and use the dissipative oil droplets to controllably encapsulate and release substances insoluble in water.We chose S-2-phenylpropionic acid as precursor and EDC as fuel to construct the dissipative liquid-liquid phase separation assembly system,and successfully formed the oil droplets to encapsulate the hydrophobic substances such as 1,3,5trifluorobenzene and 4-bromobenzotrifluoride.With the consumption of fuel,the oil droplets gradually disappeared,and the hydrophobic substances would be separated from the system again.This process was monitored in real time by 19F-NMR spectroscopy.