Sugahara Tadashi, Ichihashi Haruna, Tsumura Kana, Hara Teruyuki, Miyazaki Atsushi, Sakai Takaya
Material Science Research, Kao Corporation, 1334 Minato, Wakayama-shi, Wakayama 640-8580, Japan.
Analytical Science Research, Kao Corporation, 1334 Minato, Wakayama-shi, Wakayama 640-8580, Japan.
Langmuir. 2024 Oct 15;40(41):21719-21727. doi: 10.1021/acs.langmuir.4c02786. Epub 2024 Sep 30.
Vesicles are known to spontaneously adsorb onto solid-liquid interfaces and to form supported bilayers in aqueous solution. Cationic surfactants have typically been used to generate supported bilayers because solid surfaces in water are often negatively charged. The present study investigated the aggregation behavior of an anionic surfactant, hydroxy alkane sulfonate having a C18 alkyl chain (C18HAS) in aqueous CaCl solutions. These assessments were performed by acquiring data related to equilibrium surface tension, the solubilization of an oil-soluble dye, UV-visible transmittance, pyrene fluorescence and dynamic light scattering together with freeze-fracture transmission electron microscopy observations. The results suggest that C18HAS can form vesicles in aqueous CaCl solutions under certain surfactant concentrations. Specifically, this aggregation behavior is greatly affected by C18HAS/CaCl molar ratio. At the C18HAS/CaCl molar ratio is less than an equivalence point (that is, less than 2:1), phase separation occurs with the formation of a vesicle above solubility limit of the C18HAS Ca salt. On the other hand, in the case that the C18HAS/CaCl molar ratio is above an equivalence point (that is, above 2:1), the Na salt of C18HAS forms micelles above the critical micelle concentration (cmc), causing solubilization of vesicles. Analyses by high-speed atomic force microscopy demonstrated that the C18HAS vesicles can spontaneously form a supported bilayer on a negatively charged mica surfaces, similar to the behavior of cationic surfactant vesicles, even though C18HAS is an anionic surfactant. These results suggest that C18HAS could serve as a detergent component but also as a surface modifier when the C18HAS/CaCl molar ratio is optimized.
已知囊泡会自发吸附到固液界面上，并在水溶液中形成支撑双层膜。由于水中的固体表面通常带负电荷，阳离子表面活性剂通常被用于生成支撑双层膜。本研究考察了一种具有C18烷基链的阴离子表面活性剂——羟基烷磺酸盐（C18HAS）在CaCl水溶液中的聚集行为。这些评估是通过获取与平衡表面张力、油溶性染料的增溶作用、紫外可见透光率、芘荧光和动态光散射相关的数据，以及进行冷冻断裂透射电子显微镜观察来完成的。结果表明，在一定的表面活性剂浓度下C18HAS能够在CaCl水溶液中形成囊泡。具体而言，这种聚集行为受到C18HAS/CaCl摩尔比的极大影响。当C18HAS/CaCl摩尔比小于等当点（即小于2∶1）时，在C18HAS钙盐的溶解度极限之上会形成囊泡并发生相分离。另一方面，当C18HAS/CaCl摩尔比高于等当点（即高于2∶1）时，C18HAS的钠盐在临界胶束浓度（cmc）以上形成胶束，导致囊泡增溶。高速原子力显微镜分析表明，即使C18HAS是一种阴离子表面活性剂，但与阳离子表面活性剂囊泡的行为类似，C18HAS囊泡也能够在带负电荷的云母表面上自发形成支撑双层膜。这些结果表明，当C18HAS/CaCl摩尔比得到优化时，C18HAS不仅可以用作去污剂成分，还可以用作表面改性剂。
