Studies On The State Of Water Solubilized By The Reverse Micelles Of Quaternary Ammonium Gemini Surfactants

Quaternary ammonium Gemini surfactants are made up of two amphiphilic moieties connected at the level (or in the vicinity) of the head groups by a spacer chain. The different functional group in the spacer, the length of spacer chain and the variation of charge density of the ionic head groups will affect the water states solubilized by the reverse micelles, and can provide more information about the water states. At present, few studies are focus on the properties of Gemini surfactant in nonaqueous system. The primary work and the results are concluded as follows: The water states in the reverse micelles formed by quaternary ammoniumgemini surfactants C₁₂-s-C₁₂·2Br (s=2,3,4,5,6 and 8) or C₁₂-EOn-C₁₂·2Br (n=1,2,3) in n-heptane (add n-hexanol as cosolvent) have been investigated by FT-infrared spectroscopy. The results showed the water in C₁₂-6-C₁₂·2Br/n-hexanol/n-heptane reverse micelles could be divided into four states, corresponding to the cation-bound water, the bulk water in the reverse micelle core, the anion-bound water and the trapped water, respectively. The size of reverse micelle was small while a few amount of water was solubilized, so the water mainly existed in the form of bound water. The reverse micelle swelled and the fraction of bulk water increasd with the enhancement of water content. The bulk water was predominant when W0>20. At the same water content, the numbers of trapped water or of cation-bound water in the reverse micelles kept constant regardless of the alteration of s in C₁₂-s-C₁₂·2Br, but the numbers of anion-bound water enhanced with increasing the length of spacer, this was attributed to the ionization of counterion, the spacer of C₁₂-s-C₁₂·2Br was longer, the ionization degree of counterion was bigger. The numbers of bulk water increased with shortening the spacer, this agrees with the result that C₁₂-s-C₁₂·2Br with shorter spacer trends to form larger reverse micelles.The solubilizing ability and the properties of water in quaternary ammonium gemini surfactant (alkanediyl-α,ω-bis(dimethyldodecyl-ammonium bromides) (C₁₂-s-C₁₂·2Br, s=2,3,4,5,6 and 8)/polyoxyethylene dodecylether (C₁₂En, n=4,10,...