Design, Performance And Application Of CO₂/N₂ Switchable Microemulsions

CO₂/N₂-swicthable microemulsion was a kind of intelligent microemulsion which could reach phase separation trigerred by CO₂（showing a “off” state of microemusion） and restore to microemulsion triggered by N₂（showing a “on” state of microemulsion）. The swicthable microemulsions which had been reported could realize the transformation from microemulsion to emulsion when bubbing CO₂ and N₂ alternately, but it couldn’t reach oil-water separation. In order to solve this problem, our research group had mixed anionic surfactant with long chain tertiary amine（p Ka≥5） which were equimolar to build CO₂/N₂-switchable microemulsion which could transform from microemulsion to oil-water separation. In this paper, the universality of these kinds of CO₂/N₂-swicthable microemulsions were preliminarily explored by changing anionic surfactants, long chain tertiary amines, cosurfactants and oils. If changing one component such as surfactant, cosurfactant, long chain tertiary amine and oil by control variate method, was CO₂/N₂-switchable microemulsion still designed or not, from the particular to the general, if changing several components at same time, was CO₂/N₂-switchable microemulsion still designed or not? Microemulsion had good solubilization capacity to oil, so it was frequently usd in greasy dirt detergency. The CO₂/N₂-switchable was applied to greasy dirt detergency, the waste liquids which washed greasy dirt could reach oil-water phase separation when bubbling CO₂ because of the CO₂/N₂-swicthable microemulsions’ properties and it was possible to make oil recycle. Jiang constructed pH- responsive intelligent materials which could convert from superhydrophilic to superhydrophobic to superhydrophilic when consistently increased p H. This work gave us inspiration: if bubbling CO₂ consistently, could the CO₂/N₂-swicthable microemulsion realize the transformation from microemulsion to phase separation to microemulsion or emulsion or not, the process could be called “two responses caused by one stimulus”. On the basis of the system in whicn the anionic surfactant and long chain tertiary amine were equimolar, excess C₁₂ A was added to microemulsion which contained anionic surfactants and amines to explore the realization of “two responses caused by on stimulus” at room temperature.Main results and conclusions as follows were got by correlative experimental exploration:（1） When other components remaining unchanged, microemulsion could be got when changing surfactant, cosurfactant, amines and oil one by one; Microemulsion also could be achieved when several components changed at same time. The microemulsions above-mentioned could convert from microemulsion to phase separation to microemulsion when bubbling CO₂/N₂ alternately which preliminarily indicated universality of this series of microemulsion possibly;（2） Because SDBS had many advantages such as cheap, commercially available and acid-alkaline and hardwater resistant, the O/W microemulsion in which SDBS and C₁₂ A were equimolar was applied to greasy dirt detergency of simulated oil sands, industrial oil sands and marking pen soiled clothes. The results showed that the microemulison could remove alkanes from porous solid and fabric excellently, but the ability to wash industrial oil sands was expected to improve. The decontamination ability to marking pen solid cloth was better than commercially available washing powder solution. The microemulsion had a good ability to remove the alkanes oil and marking pen oil from the surface of the porous solid and fabric.（3） When mole ratio of SDS to C₁₂ A was 1:5, the microemulsion could realize “two responses caused by one stimulus” which converted from O/W microemulsion to phase separation to W/O emulsion by bubbling CO₂ consistently; when bubbling N₂, the system could transform from W/O emulsion to phase separation to O/W microemulsion.