Abstract

The aggregation and adsorption properties of metallosurfactant, benzyldimethylhexadecylammonium tetrachloromanganate(II) (BDHA₂[MnCl₄], where BDHA represents benzyldimethylhexadecylammonium group) in binary aqueous mixtures of ethylene glycol (EG) were investigated by tensiometric, conductometric, dynamic light scattering (DLS) and transmission electron microscopy (TEM) methods at 298.15 K. The percentage of EG (by weight) was varied between 0 and 100%. The physicochemical properties determined and discussed include critical micelle concentration (cmc), counterion binding constant (β), Gibbs free energy of micellization ($\Delta G_m^0$), surface excess at cmc (${\mathrm{\Gamma }}_{\mathit{cmc}}$), minimum area per surfactant molecule ($A_{\min }$), surface pressure (π_cmc), minimum free energies (G_min) and size of aggregates. This study revealed that with increase in percentage of EG the cmc of BDHA₂[MnCl₄] metallosurfactant increases and the cmc of BDHA₂[MnCl₄] in EG is about 158 times higher than that in water. The counterion binding constant values increase with increase in percentage of EG from 10% to 70% and thereafter decrease. The adsorption of metallosurfactant at the air–solution interface decreases as the EG content in the bulk increases. The $\Delta G_m^0$ values were found to be negative and the negative value decreases with increase in percentage of EG. Gordon parameter and ratio of surface tension of medium to that of the metallosurfactant solution at cmc are used to represent solvophobicity of the medium. DLS measurements revealed that the hydrodynamic diameters (d_H) of the micelles increase with increase in percentage of EG (in pure EG, d_H = 28.3 nm). TEM measurements showed the presence of spherical micelles.

摘要

通过张力测量、电导测量、动态光散射 (DLS)研究金属表面活性剂、苄基二甲基十六烷基四氯锰酸铵 (II) (BDHA ₂ [MnCl ₄ ]，其中 BDHA 代表苄基二甲基十六烷基铵基团) 在乙二醇 (EG) 的二元水性混合物中的聚集和吸附性能和透射电子显微镜 (TEM) 方法在 298.15 K。EG 的百分比（按重量计）在 0 到 100% 之间变化。确定和讨论的物理化学性质包括临界胶束浓度（cmc）、反离子结合常数（β）、胶束化的吉布斯自由能（$\Delta G_{米}^0$), cmc 处的表面过剩 (${\mathrm{\Gamma }}_{\mathit{厘米}}$), 每个表面活性剂分子的最小面积 (${\mathrm{一种}}_{\mathrm{分钟}}$)、表面压力 (π _cmc )、最小自由能 ( G _min ) 和聚集体的大小。该研究揭示，在EG的百分比的增加CMC BDHA的₂ [的MnCl ₄ ] metallosurfactant增加并且CMC BDHA的₂ [的MnCl ₄ ]在EG比在水中高约158倍。反离子结合常数值随着 EG 百分比从 10% 增加到 70% 而增加，然后减少。随着本体中EG含量的增加，金属表面活性剂在空气-溶液界面的吸附减少。这$\Delta G_{米}^0$值被发现是负的，负值随着 EG 百分比的增加而减少。Gordon 参数和介质表面张力与 cmc 处的金属表面活性剂溶液的表面张力比用于表示介质的疏溶剂性。DLS测量显示，该流体动力学直径（d _ħ胶束）与EG的百分比增加而增加（在纯EG，d _ħ = 28.3纳米）。TEM 测量表明存在球形胶束。