Binary Surfactant Mixed System Of Surface Activity And Synergistic Effect Research

The works mainly discussed surface properties,molecular interaction parameter andthermodynamic parameters in surfactant solution of polyoxyethylene （20） sorbitan ester （Tween）,oleylpolyoxyethylene(Brij97, AEO₂₀), ucrose stearate and Lecithin. And the emulsification,solubilising power of these surfactants and their mixtures were studied too. We hope theseresults provide s^o_me basic data to their further applications. This work mainly contains threeaspects of details:（1）The molecular interaction parameter （β^m）, molecular exchange energy（εm） andthermodynamic parameters（ΔG^o_m,ΔH^o_m,ΔS^o_m） of mixed micelle for the binary systems ofpolyoxyethylene （20） sorbitan ester （Tween） and oleylpolyoxyethylene（10）（Brij97） werecalculated fr^o_m surface tension data. The effects of the molecular structure of Tweens, thec^o_mpositions of the mixed system and the temperature were discussed. For the systemsinverstigated, it has been showed that （ⅰ）along with the increase of carbon number, the changesof the CMC andγCMCat different mole franctions in different mixture systems are different. Atα₁= 0.17, the interaction parameterβ^m< 0 , and the synergism and mole fraction of Tween （X1m） inmixed micelles increase with increase in the carbon chain of Tween, but atα₁= 0.5,0.83, theinteraction parameterβ^m> 0. And the double bond in the carbon chain decreases the synergismin the mixed micelle. So the Tween60 / Brij97 system have the strongest interaction. （ⅱ） thesurface activities have little change atα₁< 0.5 in the four mixed systems along with the increaseof the mole fraction,but the condition is opposite. The surface activites of Tween80 / Brij97mixed system has largest influence by mole fraction. The larger the mole fraction of Tween （α₁）,the greater the free energy （ΔG^o_m） in Tween60 / Brij97 mixed surfactants. Atα₁≤0.33, themixtures show synergism at mixed micelle formation, and the least interaction parameterβ^m=-7.72, yet whenα₁﹥0.33 mixtures do not have synergism. In Tween80 / Brij97 mixed system,show synergism atα₁≤0.67, and the larger the mole fraction of Tween80, the greater of thesynergism , and theβ^m= -5.97 atα₁= 0.67. It is noted that two break point are observed in thesurface tension plots of pure Tween40, Tween60, Tween80 and there mixed systems with Brij97.（ⅲ） the surface tension plots appear large difference result fr^o_m the temperature, and the surfaceactivites ,ΔH^o_m、ΔS^o_min the Tween20,Tween80 / Brij97 mixed systems increase with increasethe temperature. the critical micelle concentration,γCMC, free energy in three mixed systems and synergism in Tween60/Brij97 mixed micelle decrease as the temperature increase, but theenthalpy and entropy are reverse in Tween60/Brij97. the free energy of Tween80 are differentfrom others , and the interaction of this mixed system has different change with the temperatureincrease at different mole fraction.（2） The surface properties and thermodynamic parameters of micellization for binarysystems of oleylpolyoxyethylene（10）（Brij97） / sucrose stearate, oleylpolyoxyethylene（20）(AEO₂₀) / sucrose stearate and Brij97/ Lecithin were calculated from surface tension data. Theeffect of temperature on mixed systems which molar fraction is 0.5 were discussed. The resultsreveal that the four investigated systems show non-ideality in the micelle formation .The foursystems have been showed （ⅰ） Compared with AEO₂₀, Brij97can enhance the surfaceproperties of sucrose stearate obviously. the larger the mole fraction of Brij97, the decreasingerthe CMC ,γCMC, surfacr adsorption and free energy （ΔG^o_m） of micellization in Brij97 / sucrosesteatite mixed surfactants, and the free energy of AEO₂₀/ sucrose steatite have the same changewith Brij97 / sucrose steatite mixed systems. The interaction of the two mixed systems aredifferent, atα1≥0.74, there are synergism, and at 0.11≤α1≤0.5, display repulsion effect inAEO₂₀/ sucrose steatite systems. In Brij97 / sucrose steatite mixed surfactants show repulsioneffect only in all mole fraction, but they do not calculated by Rubingh. （ⅱ） The surfaceproperties and the capacity of forming micelle of Brij97 are decreased by Lecithin and sucrosesteatite, and the effect of Lecithin on Brij97 is obvious, CMC and free energy of micelle areincrease obviously with the mole fraction increased. Sucrose steatite and Brij97 enhance thesurface properties of Lecithin obviously, and the effect of Brij97 is larger, the CMC andγCMChave change most in the Brij97/ Lecithin ,and theΔG^o_mdecreased, forming micelles easily. （ⅲ）in the range of 25oC to 45oC, the CMC,γCMCand free energyΔG^o_mdecrease of the three mixedsystems as the temperature increase, that is the surfact properties are enhanced and form micelleeasily with the temperature increased. The enthalpyΔH^o_mand entropyΔS^o_mhave differentsituations in three mixed systems as temperature increase. At 298 K, Brij97 / sucrose steatiteshow synergism.（3） All surfactants are discussed display emulsifying capacity with isopropyl myristate（IPM）, and the best emulsifier is Tween80, and the second is sucrose steatite. The emulsifyingcapacity is enhanced as the temperature increasing. Brij97, AEO₂₀, sucrose stearate, Lecithin and there mixed micelles for solubility enhancement of curcumin are discussed, the rusults show that,AEO₂₀is best solubilizer of the four surfactants, and the second is Lecithin. The surfactantsmixtures show good solubilising power too, and the order is Brij97 / Brij97, AEO₂₀/ sucrosestearate and so on.