| Bicontinuous microemulsion,which is also called middle-phase microemulsion,is an intermediate phase during the transition between Winsor I and Winsor II type microemulsions.Compared with droplet microemulsions,bicontinuous microemulsions have some unique features,such as high solubilization capacity toward both oil and water,ultralow interfacial tension,large interfacial area and low mass transfer resistance.These features make bicontinuous microemulsion a promising medium in the fields of biocatalysis and biotransformation.Due to low vapor pressure,high chemical/thermal stability and so on,ionic liquids have recently attracted considerable attention of researchers.Compared with organic solvents,ionic liquids can be considered as "designer green solvents".The constructions and applications of hydrophobic ionic liquid(HIL)based droplet type microemulsions have been reported,however,less attention has been paid to the HIL-based bicontinuous microemulsions,especially biocompatible ones.At present,some HIL-based bicontinuous microemulsions stabilized by nonionic surfactant are available,however,those stabilized by ionic surfactantshave not been reported.In this thesis,two attempts have been made:1.Additive effects on the phase behavior and interfacial properties of cationic surfactant([C16mim]Br)stabilized hydrophobic ionic liquid based middle-phase microemulsionsThe ?-? fishlike phase diagram of the system[C,6mim]Br/[Omim]Tf2N/water was constructed in the presence of different additives(alcohol and inorganic salt).From the diagram some additive-dependent characteristic physicochemical parameters were obtained.Results show that with the increase of the alkyl chain length of alcohols,the optimum solubilization parameter(SP*)decrease,while the maximum alcohol width(??)for the phase inversion and the mass fraction of the alcohol in the balanced interfacial film(Ain)increase.For inorganic salts,an increase in[NaCl],or an increase of the radius of halides(X-)at constant[NaX],or the substitution of the divalent anion SO42-,by the same molar concentration of monovalent anion Cl-makes both SP*and ?? increase,but Ain decrease.Overall,the alcohol effect on the phase behavior of the microemulsion is greater than the salt effect and the composition effect of an inorganic salt is greater than the concentration effect.These effects could be rationalized based on their influence on the dissolution and aggregation behavior of the surfactant[C16mim]Br in the system.2.Phase behavior of zwitterionic surfactant stabilized hydrophobic ionic liquid based middle-phase microemulsions and the effect of interfacial properties of microemulsion on the kinetic parameters of the solubilized lipaseThe ?-? fishlike phase diagram of sulfobetaine zwitterionic surfactant(SB)/HIL/Tris-HCl(pH = 8.3)/alcohol systemwasconstructed,and theinfluencesof different components(surfactant,alcohol and HIL)on the phase behavior and interfacial compositionswere investigated.The results show that the surfactant with long alkyl chain length,or alcohol with short alkyl chain length,or hydrophobic ionic liquid with low energy density,is conducive to improvingthe optimum solubilization parameterof SB and the alcohol partitioning in the interfaceof the microemulsion.The influence of the resulting interfaceon the kinetic parameters of the solubilizedlipase was also studied at 35.0 ?.The results show that for interfaces composed by SB-12 andn-pentanol,the catalytic efficiency of lipase depends on the HIL.The[Omim]Tf2N-based bicontinuous microemulsion(kcat/Km = 0.960 mM-1 min-1)has largercatalyticefficiencythan[Omim]PF6-based one(kcat/Km = 0.582 mM-1 min-1).Analysis indicates that it is caused by the HIL;different HIL results in different interfacial compositions,and therefore different lipase activities.The present results will help us to construct a microenvironment that is suitable for the expression of the catalytic efficiency of a soulubilized enzyme via theregulation of the interfacial properties of the resulting microemulsion. |
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