Research On Vegetable Oils-based Aprotic Ionic Liquid Microemulsions

The researches of ionic liquids(ILs) involved microemulsion systems provided theoretical foundation and technical support for the application of ILs in chemistry and chemical engineering, but the research mainly restricted to the framework of traditional petroleum oil-based IL microemulsions. Currently, with the increase of the environmental protection consciousness of people, air pollution caused by the heavy use of petroleum oil has attracted great attention. Vegetable oils with renewable and biodegradable merits are not only promising alternatives to petroleum oil-based lubricants, but also substitutes of the oil phase in water/oil or IL/oil microemulsions.In this paper, microemulsions with vegetable oil as the non-polar phase and aprotic IL as the polar phase were successful formed. Effects of the oiling kind, IL anion structure, alkyl chain length of IL cations, surfactant structure, mass ratio of surfactant to co-surfactant, alkanol chain length of co-surfactant, temperature and integrated surfactants on the phase behaviors and phase-forming capacities of the vegetable oil-based IL microemulsions were investigated comprehensively and systematically. The results were summarized as follows:(1) The alkyl chain length and space location-obstruct effect of vegetable oils were able to affect the phase-forming capacities of IL microemulsions;(2) Strong electronegativity of IL anions made the formation of microemulsions easier;(3) Increasing the length of the alkyl chain of IL cations from C2 to C6 increased the ability to form microemulsions;(4) Surfactant had a IL-oil amphiphilic balance value, which could be altered by the addition of co-surfactant;(5) The spontaneity of the microemulsification would grow up with the increment in the chain length of alcohol from C2 to C6, followed a decrease with the extension chain length to C8;(6) Vegetable oil-base aprotic IL microemulsions preferentially formed at higher temperatures;(7). The addition of [C8mim][Cl] could increase the single-phase region area effectively, and the higher the [C8mim][Cl] dosage, the larger the single-phase region area is.A series of reverse vegetable oil-based aprotic IL microemulsions stabilized by single surfactant and integrated surfactans were constructed, and the effects of their conductivity behaviors, micro-circumstance polarities, size scale and distributions, viscosity-temperature characteristics and tribology properities were investigated systematically. The results were summarized as follows: For the single surfactant stabilized IL microemulsions,(1) they showed the transform of oil-in-IL(O/IL) to bicontinuous(BC) to IL-in-oil(IL/O) microstructure with the increasing of oil content;(2) The droplets in IL/O microemulsions were observed to be monodisperse in nature, and the sizes of the aggregates increased linearly with increasing polar phase content;(3) Methyl orange, which was the color probe, were solubilized inside the IL pool of IL microemulsions. The micro-polarity of IL/O microemulsions increased gradually with the addition of IL, but remain samller than that of pure IL;(4) The interaction between the oxygen atoms of OE units from the ends of TX-100 and the hydrogen atom of imidazolium ring from aprotic IL was confirmed to be the driving force of designed microemulsions;(5) The designed IL microemulsions showed no stratified phenomenon under the test temperature, and their viscosity-temperature characteristics increased with increasing IL content;(6) The average friction coefficient of the IL/O microemulsions fluctuated with increasing friction time, and showed better antiwear properties than that of commercial 400SN; For the integrated surfactants stabilized IL microemulsions,(1) the addition of [C8mim][Cl] could reduce the degree of difficulty to form IL/O microemulsions, decrease the average friction coefficient, and improve the viscosity-temperature characteristics,(2) The exchange of [Cl]- with [BF4]- occurred on the interface, and facilitated the driving force of microemulisons formation.The interfacial composition, structure parameters, and thermodynamic properties for castor oil(CO)-based, glycerol trioleate(GT)-based, and epoxidized soybean oil(ESO)-based IL microemulsions were researched by dilution method, and the effects of the cationic chain length of ILs, the oxyethylene groups‘ number of surfactants, the carbon chain lengths of co-surfactants, and temperature on the above paoameters were investigated. The results were summarized as follows:(1) Less co-surfactants at the interface were required for the formation of stable reverse CO-ILMs, GT-ILMs, ESO-ILMs with the increase in the cationic chain length of ILs, the oxyethylene groups‘ number of surfactants, and temperature, while the radius for the polar core of ILs increased and the total number of microemulsion droplets decreased correspondingly;(2) Co-surfactants could adjust the IL-oil amphiphilic balance of the interface, alclhols with shorter carbon chain were easier to transfer to the interface from oil phase, and donated better adjustment effect to the amphiphilic balance, so less co-surfactants were required at the interface;(3) The standard Gibbs free energy changes(ΔGt0for the transfer of co-surfactant from oil phase to the interface were negative in all three ionic liquid microemulsions, suggested that CO-ILMs, GT-ILMs, ESO-ILMs all formed spontaneously;(4) The formation of nonaqueous ILM systems could end up with both absorption and release of heat, and with ordered or disordered state, depending on the type of oil and thermal conditions.Copper nanoparticles were successfully in situ synthesized by single microemulsion method with [Bmim][BF4]/CO/TX-100/n-butanol as the reaction media and nontoxic ascorbic acid as the reducing agent. The friction performances of the disigned copper-based microemulsions were evaluated. The results were summarized as follows:(1) The in situ synthesized copper nanoparticles monodispered in the IL/CO systems with average sizes of 5 ~20 nm. The reaction time, reaction temperature and the theoretical concentration of copper in the nanolubricants all had certain influences on the appearance and average size of nanolubricants;(2) The specific absorbion by nanosized copper particles could be detected on the UV-vis absorption spetra;(3) Copper-based IL/CO microemulsions were highly stable at ambient condition due to the reducing and capping performance of the excess ascorbic acid, as well as the stable nature of IL microemulsions;(4) With the increasing of copper concentration, copper-based IL/CO microemulsions showed lower friction coefficients and smaller wear scar diameters, the lubricant properties of the microemulsions containing the as-prepared copper nanopariticles were improved significantly.