Aqueous Two Phase Behavior And Phase Inversion Of The Catanionic Surfactants Mixed Systems

In this thesis,aqueous two-phase behavior and phase inversion and aggregates microstructures of the mixed propanediyl-α,ω-bis(dodecyl dimethyl ammonium bromide)(12-3-122+,2Br-)/sodium dodecyl sulfonate(Na+AS-)and 12-3-122+,2X-(X-= F-,Cl-,NO3-,Ac-,1/2SO42-)/Y+AS-(Na+,K+,Rb+)systems have been investigated,and the influences of the inorganic ion specific effect,added inorganic salt and short chain alcohols on the phase behavior and phase inversion have been discussed.1.Phase behavior and phase inversion of aqueous two-phase systems with excess cationic surfactant(abbreviated as ATPS-C)formed by aqueous mixtures of 12-3-122+,2X-and Na+AS-at 318.15 K have been investigated.The top phase of ATPS-C with water or NaX aqueous solutions as solvents is the concentrated phase.ATPS-C region becomes wider and shifts far from the equimolar composition with the addition of salts.The addition of NaBr with larger density contribution than NaX leads to phase inversion of ATPS-C.For the ATPS-C with certain mole fraction of 12-3-122+,2X-in total surfactant x12-3-12+,2x-,the concentrated phase in ATPS-C inverses from the top phase to the bottom phase with increase of the concentration of NaBr.TEM micrographic experiments illustrate that there is no direct relationship between the microstructures of the concentrated phase in ATPS-C and phase inversion.Phase composition analysis results illustrate that for the ATPS-C,counterions X-in the concentrated phase is gradually replaced by Br-with addition of NaBr,and more X-ions are released to the diluted phase.That’s why the density increase of the concentrated phase is larger than that of the dilute phase in the ATPS-C with addition of NaBr;thus,phase inversion occurs.At the same concentration of NaBr,in ATPS-C with smaller x12-3-122+,2x-,the top phase is concentrated.The surface charge density of aggregates increases with the increase of x12-3-122+,2x-,leads to more Br-counterions taking the place of X-and counterion binding with the aggregates,therefore the density of the concentrated phase increases and the density of the dilute phase decreases,causing phase inversion.According to Hofmeister series and law of matching water affinity,chaotropic ion can form close ion-pair with oppositely charged chaotropic ion,while the interaction between chaotropic and oppositely charged kosmotropic ions is weak.So the counterion binding with chaotropic headgroup follows the order of Hofmeister series:1/2SO42-<F-<Cl-<Ac-<Br-<NO3-.The density contribution of counterion ions increases according to the sequence:Ac－<Cl-<F-<NO3-<1/2SO42-<Br-.The larger density contribution of X-counterion and the stronger counterion binding competitive ability of Br-against X-with aggregates are in favor of the phase inversion in ATPS-C.2.Phase inversion and phase behavior of aqueous two-phase systems with excess anionic surfactant(abbreviated as ATPS-A)formed by aqueous mixtures of 12-3-122+,2C1-and Y+AS-(or Y+L-)at 318.15 K have been investigated.The experimental results indicate that the influence of salts on the ATPS-A formed by 12-3-122+,2Cl-/Y+AS-system is greater than that on the 12-3-122+,2Cl-/Y+L-system;For the ATPS-A formed by 12-3-122+,2Cl-/Y+L-system,addition of KCl and RbCl cannot result in phase inversion;addition of KCl can result in phase inversion in ATPS-A formed by 12-3-122+,2CI-/Y+AS-systems,however,addition of RbCl cannot lead to phase inversion.To interpret the phase-inversion phenomena,the phase composition,phase density between the dilute phase and the concentrated phase in ATPS-A were investigated.Results illustrate that for the ATPS-A formed by 12-3-122+,2Cl-/Na+L-/KCl systems,the counterion binding with kosmotropic headgroup follows the order:K+<Na+,the concentration of K+ increase of the concentrated phase is smaller than that of the dilute phase,so the density increase of the concentrated phase is smaller than that of the dilute phase,thus,phase inversion do not occurs,for the ATPS-A formed by 12-3-122+,2Cl-/Na+AS-/KCl,the K+ counterions in the dilute phase are exchanged into the concentrated phase with addition of KCl,the density increase of the concentrated phase is larger than that of the dilute phase in the ATPS-A,thus,phase inversion occurs.The counterion binding with chaotropic headgroup follows the order of Hofmeister series:Na+<K+<Rb+.The density contribution of counterion ions:Na+<K+<Rb+.The larger density of Y+ counterion and the stronger counterion binding force with aggregates are in favor of the phase inversion in ATPS-C.3.Short chain alcohol-induced phase inversion of ATPS formed by aqueous mixtures of 12-3-122+,2Br-/Na+AS-at 318.15 K has been investigated.The experimental results indicate that the ATPS region shifts far from the equimolar composition and aqueous two-phase inversion occurs with the addition of alcohol.The alcohol-induced phase inversion occurs according to the sequence:butanol>propanol>ethanol.To interpret the phase-inversion phenomena of ATPS,TEM micrographic,phase density between the dilute phase and the concentrated phase in ATPS-C were investigated.TEM micrographic experiments illustrate that there is relationship between the microstructures of the concentrated phase in ATPS-C and phase inversion.With the addition of propanol,the concentrated phase in ATPS-C gradually into multilayer vesicles,and the large kernel can wrap more low-density solvent,the density of the concentrated phase decreased.Density experiments illustrate that the density decrease of the concentrated phase is larger than that of the dilute phase in the ATPS-C;thus,phase inversion occurs.With the increase of alcohol concentration,multilayer vesicles become into single vesicles,eventually spherical micelles,due to the reduced hydrophobic interaction.