Coacervate Microdroplets Based On Ruthenium Complexes And Their Dynamic Properties

Life is a highly dynamic and unbalanced system that requires continuous energy acquisition from the external environment to maintain the balance of internal complex reaction networks.For example,plants need a continuous supply of solar energy,carbon dioxide,and water to carry out photosynthesis and sustain life activities.In order to explore the origin of life systems,researchers have established protocell models in a prebiotic environment.Protocells can provide independent reaction sites for complex chemical systems and regulate them in both time and space.An ideal primitive cell model should have a non-equilibrium state and be able to generate dynamic behavior driven by chemical reactions.Common primitive cell models include phospholipid vesicles,protein microcapsules,polymer capsules and coacervate microdroplets.Due to the absence of a closed membrane structure,coacervate microdroplets driven by liquid-liquid phase separation can undergo rapid material exchange with the external environment and have a reversible dynamic behavior of assembly and disassembly.Based on the above background,this thesis investigates the oscillation and reaction diffusion equilibrium phenomena of ruthenium complex coacervate microdroplets in complex environments,and successfully develop a novel dynamic soft material system.The research content and results of this article are mainly divided into the following three parts:(1)Redox driven oscillation behavior of ruthenium complex coacervate microdroplets: A class of ruthenium complex surfactant molecules was designed and induced to undergo liquid-liquid phase separation in aqueous solution by sodium nitrate.The ruthenium complexes based coacervate microdroplets were constructed and the role of electrostatic repulsion and hydrophobic aggregation in the coacervation process was revealed.The coacervate microdroplets formed by the aggregation of ruthenium complexes can selectively recruit molecules within them,raising the local concentration of molecules,and promoting the rate of enzymatic hydrolysis reactions.The influence of counter-ion association and host guest interaction on condensed droplets indicates that the ability of ruthenium complexes to form coacervate microdroplets through liquid-liquid phase separation is caused by the charge repulsion between the charged head groups of surfactant molecules and the hydrophobic action of the hydrophobic alkyl chain tails.During the transition of the ruthenium complex from the reduced state to the oxidized state,the repulsive force between the charged head groups of the ruthenium complex gradually increases,driving the coacervate microdroplets in the mixed solution to transform into small micelles.The volume of the coacervate microdroplets exhibits a dynamic behavior of first swelling,then contracting,and finally disintegrating.When ruthenium complexes are used as catalysts in the Belousov-Zhabotinsky(BZ)reaction system,they undergo periodic cycles between the reduced and oxidized states.Redox drives the periodic formation and disintegration of coacervate microdroplets in the mixed solution,leading to periodic oscillations in the turbidity of the solution.The oscillation experiment of the coacervate layer on the surface of silica microspheres and polystyrene microspheres proves that the oscillation reaction driven by oxidation and reduction can occur simultaneously in the solution and at the interface.The coacervate microdroplets can dynamically encapsulate hydrophobic polystyrene microspheres through the oscillation behavior.Under the action of redox driven oscillatory behavior,micron sized coacervate microdroplets can pass through nanoscale channels,reminiscent of the deformation behavior of red blood cells in blood vessels.(2)Formation of complex coacervate microdroplets induced by photopolymerization: As a photocatalyst,ruthenium complex can be used to initiate free radical polymerization of ethylene monomers in aqueous solution with the co initiator tetramethylethylenediamine.When the monomer is acrylic acid,the negatively charged polyacrylic acid generated by the polymerization reaction can be separated from the positively charged ruthenium complex by electrostatic interaction to form coacervate microdroplets.As the illumination time increases,the coacervate microdroplets in the mixed solution grow with time,and the turbidity of the solution also increases.By introducing other monomers into the polymerization system to copolymerize with acrylic monomers,the size of the coacervate microdroplets can be controlled,and the coacervate microdroplets can also have the function of biological recognition.When cross-linking agents are introduced into the polymerization system,fusion experiments and photobleaching recovery experiments have demonstrated that coacervate microdroplets undergo phase transitions from liquid to solid,which can be used as a biomimetic model for the liquid-liquid phase separation and aging process in living systems.When the light driven polymerization system is introduced into the agarose water gel,coacervate microdroplets can also be formed in the gel network,and the growth range of coacervate microdroplets can be patterned through the mask,providing a new research system for the field of light signal transmission.(3)Dynamic behavior of light driven coacervate microdroplets: Changes in the light range can regulate the formation range of polyacrylic acid.Mixed solutions outside the light range do not contain polyacrylic acid,so the growth range of coacervate microdroplets remains consistent with the light range.However,due to the effect of concentration difference,polyacrylic acid will diffuse outside the light range,and the coacervate microdroplets are in a nonequilibrium growth environment.Therefore,the size distribution of coacervate microdroplets within the illumination range is uneven,and the average particle size of coacervate microdroplets near the center of the circle is about 2.91 μm.The average particle size of coacervate microdroplets at the edge of the illumination range is only 0.78 μm.After stopping illumination,the photocatalytic polymerization reaction stops,and the coacervate microdroplets formed within the illumination range gradually disintegrate due to the diffusion of polyacrylic acid molecules.The disintegration of coacervate microdroplets can be inhibited by using monomers with sulfonic acid side groups or introducing cross-linking agents into the polymerization system.By controlling the time and frequency of illumination,it is possible to control the nonequilibrium behavior of the growth and disintegration of coacervate microdroplets.The oscillatory growth of coacervate microdroplets can occur simultaneously at the interface between the solution and the colloid,and the growth of coacervate microdroplets at the interface with different properties can lead to differences in the spatial relative positions of coacervate microdroplets and polystyrene microspheres.