Soft Materials Research Laboratory, Department of Chemistry, National Institute of Technology, Calicut, India.
J Phys Chem B. 2011 Jan 27;115(3):464-70. doi: 10.1021/jp1043255. Epub 2010 Dec 30.
A micelle-vesicle transition induced by n-octanol C(8)OH was observed in an aqueous cetyltrimethylammonium bromide (CTAB)/potassium bromide (KBr) system. This transition was investigated by viscosity, rheology, dynamic light scattering (DLS), and direct imaging technique, cryo-transmission electron microscopy (cryo-TEM). Viscometry shows that the system underwent several morphological transitions with the increase in concentration of C(8)OH (regions I-IV). At low octanol concentration (region I), DLS analysis showed an increase in the apparent hydrodynamic diameter of the micelles with the addition of C(8)OH which was supported by cryo-TEM and rheology. With further addition of C(8)OH, transition of the elongated micelles occurred to a viscoelastic fluid comprising entangled wormlike micelles (region II), for which rheological data can be described by the Maxwell model. Further, the wormlike micelles transform to vesicles at [C(8)OH] ≈ 0.020 M (region III). This transition and the consequent changes in the fluid response can be explained in terms of vesicle formation caused by further addition of C(8)OH. Beyond this concentration (region IV), vesicles are the predominant microstructures in the system which shows unusual temperature response.
在水相十六烷基三甲基溴化铵（CTAB）/溴化钾（KBr）体系中，观察到由正辛醇 C（8）OH 诱导的胶束-囊泡转变。通过粘度、流变学、动态光散射（DLS）和直接成像技术、冷冻传输电子显微镜（cryo-TEM）研究了这种转变。粘度测量表明，随着 C（8）OH 浓度的增加，该体系经历了几个形态转变（区域 I-IV）。在低辛醇浓度（区域 I）下，DLS 分析表明随着 C（8）OH 的加入，胶束的表观水动力直径增加，这得到了 cryo-TEM 和流变学的支持。随着 C（8）OH 的进一步加入，长形胶束发生转变为包含缠结的蠕虫状胶束的粘弹流体（区域 II），流变学数据可以用 Maxwell 模型来描述。此外，在 [C（8）OH] ≈ 0.020 M 左右（区域 III），蠕虫状胶束转变为囊泡。这种转变和随后流体响应的变化可以用 C（8）OH 的进一步加入引起的囊泡形成来解释。超过这个浓度（区域 IV）后，囊泡是体系中主要的微观结构，表现出异常的温度响应。
