Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
J Phys Chem B. 2012 Feb 23;116(7):2065-74. doi: 10.1021/jp210467p. Epub 2012 Feb 14.
The semiempirical kinetic method has been used to determine the ratio of cetyltrimethylammonium bromide, CTABr, micellar binding constants of counterions X (K(X)) and Br (K(Br)), i.e., K(X)/K(Br) (= R(X)(Br)) for X = dianionic 5-methyl- and 5-methoxysalicylate ions. The values of K(X) and K(Br) have been derived from the kinetic parameters obtained in the presence of spherical/nonspherical and spherical micelles, respectively. The values of R(X)(Br) remain essentially independent of [CTABr] within its range 0.005-0.015 M for both dianionic 5-methyl- and 5-methoxysalicylate ions. The increase in temperature from 35 to 55 °C decreases the values of R(X)(Br) from 796 to 53 for 5-methylsalicylate ions and from 89 to 7.0 for 5-methoxysalicylate ions. Rheological properties of 0.015 M CTABr solutions containing ≥0.01 M counterionic salt, M(2)X, show indirectly the presence of unilamellar vesicles, ULV, and long linear, entangled, and branched wormlike micelles, WM, at, respectively, 35 and 55 °C for X = dianionic 5-methylsalicylate ion. However, such studies show WM and probable spherical micelles, SM, at, respectively, 35 and 55 °C for X = dianionic 5-methoxysalicylate ions. It has been shown that, at a constant [CTABr], the micellar structural transitions from SM-to-WM-to-vesicles may be correlated quantitatively with the values of R(X)(Br) regardless of whether such micellar structural transitions occur due to variation in the values of [M(2)X] at a constant temperature or due to variation in temperature at a constant [M(2)X].
已使用半经验动力学方法确定了十六烷基三甲基溴化铵（CTABr）与抗衡离子 X（K(X)）和 Br（K(Br)）的胶束结合比，即 X = 二阴离子 5-甲基和 5-甲氧基水杨酸离子的 K(X)/K(Br)（= R(X)(Br)）。K(X)和 K(Br)的值分别来自于在分别存在球形/非球形和球形胶束时获得的动力学参数。对于二阴离子 5-甲基和 5-甲氧基水杨酸离子，R(X)(Br)的值在 0.005-0.015 M 的范围内基本上与[CTABr]无关。从 35°C 升高到 55°C，R(X)(Br)的值从 5-甲基水杨酸离子的 796 降至 53，从 5-甲氧基水杨酸离子的 89 降至 7.0。在 0.015 M CTABr 溶液中，当含有≥0.01 M 抗衡离子盐 M(2)X 时，流变性质间接表明存在单分子层囊泡（ULV）和长线性、缠结和分支的蠕虫状胶束（WM），分别在 35 和 55°C 时 X = 二阴离子 5-甲基水杨酸离子。然而，对于 X = 二阴离子 5-甲氧基水杨酸离子，这些研究表明在 35 和 55°C 时分别存在 WM 和可能的球形胶束（SM）。已经表明，在恒定[CTABr]下，从 SM 到 WM 到囊泡的胶束结构转变可以与 R(X)(Br)的值定量相关，无论这种胶束结构转变是由于在恒定温度下[M(2)X]值的变化还是由于恒定[M(2)X]温度的变化引起的。
