长链阳离子表面活性剂蠕虫状胶束的剪切带转变行为研究

Shear Banding Transition of Wormlike Micelles Formed by a C_(22)-Tailed Cationic Surfactant

报道一种含有不饱和疏水尾链的超长链阳离子表面活性剂——N-芥酸酰胺丙基-N,N,N-三甲基碘化铵(EDAI)自组装所形成的蠕虫状胶束及其剪切带行为.EDAI浓溶液表现出了明显的剪切带转变特征,即溶液的流动曲线被介于两个临界剪切速率之间的剪切应力平台分割为粘度不同的两部分.在剪切带转变区域,原本均质的流体表现出机械剪切不稳定性,沿速度梯度方向被分割为剪切速率不同的两个宏观流体层.

Both fundamental and technological research interests highlighted in the past few decades on surfactant self-assembly wormlike micellar aggregates. We report herein the shear-banding transition of wormlike micelles formed by a novel C22-tailed cationic surfactant, N-erucylamidopropyl-N,N,N-trimethylammonium iodide （EDAI） in aqueous solution. Steady and dynamic rheological measurements indicate that concentrated EDAI solution is strongly viscoelastic, which can be attributed to the presence of wormlike micelles in the solution. Rheological tests implies that the concentrated EDAI worm solution shows typical characteristic of shear banding transition, i.e., the flow curve is composed of two branches corre- sponding to high and low viscosities separated by a stress plateau between two critical shear rates. In the shear banding tran- sition region, the fluid is mechanically unstable and the initial homogeneous flow was spurted into two macroscopic layers bearing different shear rates and stacked along the velocity gradient direction. The shear-banding transition behavior was further directly observed on a visualization rheometer.