Cao Xiaoqin, Guo Weiluo, Zhu Qi, Ge Hongjiang, Yang Hua, Ke Yubin, Shi Xiaohuo, Lu Xingyu, Feng Yujun, Yin Hongyao
Polymer Research Institute, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, PR China.
CNPC Bohai Drilling Engineering Co., Ltd, Tianjin 300450, PR China.
J Colloid Interface Sci. 2023 Nov;649:403-415. doi: 10.1016/j.jcis.2023.06.086. Epub 2023 Jun 17.
Worm-like micelles are susceptible to heating owing to the fast dynamic exchange of molecules between micelles. Inhibition of such exchange could afford robust worm-like micelles, which is expected to largely improve rheology properties at high temperatures.
A cationic surfactant docosyl(trimethyl)azanium chloride (DCTAC) and a strongly hydrophobic organic counterion 3-hydroxy naphthalene-2-carboxylate (SHNC) were used for the worm-like micelles fabrication. The microstructure was characterized using cryogenic transmission electron microscopy and small-angle neutron scattering, and the interactions between DCTAC and SHNC were characterized using nuclear magnetic resonance spectroscopy. Rheometer was employed to measure the rheological properties of the solution.
SHNC/DCTAC at the molar ration of 1:2 forms ultra-stable worm-like micelles, whose viscosity remain stable at temperature up to 130 °C. SHNC is found to strongly adsorbs on DCTAC micelle with the orientation on the surface of micelle, keeping the naphthalene backbone entire penetration into the palisade layer while both carboxylic and hydroxyl groups protrude out of the micelle. With temperature increasing, this adsorption further strengthens, resulting in the growth contour length and accompanying the enhancement of rheological properties. One SHNC molecule and two DCTAC molecules are speculated to form a stable complex via multiple interactions including hydrophobic, cationic-π, and π-π interactions, which decreases the dynamic exchange of them between micelles. These findings are helpful to understand surfactant aggregates stability and assist the development of novel stable supramolecular nanostructures. Additionally, the excellent thermal stability of this worm-like micellar fluid makes it a potential high-temperature resistant clean fracturing fluid for deep oil reservoirs.
由于胶束间分子的快速动态交换，蠕虫状胶束易受热影响。抑制这种交换可得到稳定的蠕虫状胶束，有望在很大程度上改善高温下的流变性能。
使用阳离子表面活性剂二十二烷基三甲基氯化铵（DCTAC）和强疏水性有机抗衡离子3-羟基萘-2-羧酸盐（SHNC）制备蠕虫状胶束。用低温透射电子显微镜和小角中子散射对微观结构进行表征，用核磁共振光谱对DCTAC和SHNC之间的相互作用进行表征。采用流变仪测量溶液的流变性能。
摩尔比为1:2的SHNC/DCTAC形成超稳定的蠕虫状胶束，其粘度在高达130℃的温度下保持稳定。发现SHNC强烈吸附在DCTAC胶束上，其取向在胶束表面，萘骨架完全穿透到栅栏层中，而羧基和羟基都突出于胶束之外。随着温度升高，这种吸附进一步增强，导致轮廓长度增加，并伴随着流变性能的增强。推测一个SHNC分子和两个DCTAC分子通过包括疏水、阳离子-π和π-π相互作用在内的多种相互作用形成稳定的复合物，这减少了它们在胶束间的动态交换。这些发现有助于理解表面活性剂聚集体的稳定性，并有助于新型稳定超分子纳米结构的开发。此外，这种蠕虫状胶束流体优异的热稳定性使其成为深部油藏潜在的耐高温清洁压裂液。
