Studies On The Surfactants Based On Tea Saponins Molecular Modification

Tea saponins is an exceptional natural surfactant resource isolated from the seedsof Camellia oleifera after oil production, it is an nonionic surfactant and has been usedfor centuries in China. Because of increasing demand for green surfactants,development of surfactants based on natural resources is highly desirable. However,owing to its structural complication, studies on modification of tea saponins haveseldom been practiced. Tea saponins molecular has been modified in this research andthe structure and surface activity of tea saponins derivatives were investigated.The component of the raw material tea saponins(TS) was obtained by usingMALDI-TOFMS, which shows that TS was composed of four different monomers.With similar properties of several kinds of monomers, and the purpose of seekingsimple modification methods, obtaining the practical green surfactants, we adopted thetea saponins compounds as raw materials. TS which was sulfated by Pyridine sulfurtrioxide complex was converted into TSS, the structure and surface properties such ascmc, foam stability, stability in hard water and emulsifying power of TSS wereinvestigated. Compared with that of TS, γCMCof the new surfactant, TSS, did notchange appreciably but with a notable decrease of CMC, both CMC and γCMCwereincreased with increasing of substitution degree. The foaming properties of TSS-1wasbetter than TS, TSS-5was the same with TS while TSS-10became very poor. Theemulsifying power of the three TSS was better than TS. The ability of TSS-1could beenhanced by DAC when they have a appropriate ratio of n(TS): n(DAC)=1:2.Tea saponins succinic ester (TS-Su), was obtained through the esterification of TSwith succinic anhydride under alkaline condition, TS-Sus with different succinylationdegree can shuttle between nonionic and anionic surfactants. TS-Su of the1:10ratio hasalmost reached the maximum degree of succinylation, γCMCof Ts-sus were increasedwith increasing of substitution degree and excellent hard water resistance was showedunder acidic condition. Variation of pH had dramatic effect on surface tension of TS-Sus,especially during the pH range of4-5.5the surface tension increased sharply. The foamproperties of TS-Sus decreased with the increase of degree of succinylation and betterfoaming properties was displayed under acid condition than basic condition. Theemulsifying power of TS-Sus was decreased with increasing of substitution degree. Theexperiments indicated that the different properties showed in various environmentscould improve the scope of application. TS aliphatic ester (TSA) with varying carbon chain was synthesized by reaction ofTS and aliphatic acyl chloride. The optimum reaction ratio of acyl chloride and TS wasstudied with the lauroyl chloride as the representative, which shows that the optimizedcondition was1:4. Influence of the length of hydrophobic group on the surface activityhas been studied in brief, the results show that surface activity is significantly concernedwith the length of hydrophobic group, and changes with the chain length show a certainregularity.