Shuangjian Dong, Yunling Li, Yongbo Song
Jan 26, 2013
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0
Influential Citations
20
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Journal
Journal of Surfactants and Detergents
Abstract
The unsaturated long-chain carboxybetaine and hydroxy sulfobetaine were synthesized by the reaction of unsaturated octadecyl tertiary amine with sodium chloroacetate and 3-chloro-2-hydroxypropanesulfonic acid sodium salt, respectively. The structures of the two betaines were characterized by IR and 1H-NMR spectroscopy. The Krafft points of the two betaines are below 0 °C and the isoelectric points are at pH 8.2 and 8.0, respectively. The surface tensions (γCMC) at the critical micelle concentrations (CMC) were measured to investigate the surface activities of the prepared compounds when the pH is equal to 4.0, 6.5 and 10.0 at 50 °C, respectively. Meanwhile, the corresponding saturated betaines were synthesized and determined for comparison. The double bond in the non-polar tail leads to a slightly higher CMC and a lower γCMC. Though the CMC of the unsaturated betaine is slightly higher than that of saturated betaine for the double bond in the non-polar tail, the applied range of the unsaturated betaine is broader than corresponding saturated betaine for low Krafft point. The CMC and ГCMC of the four betaines increase, but the pC20 decreases, with increasing pH. As a whole, the impact of pH on the performance of the four betaines is not very obvious.