Relating shear banding, structure, and phase behavior in wormlike micellar solutions
Relating shear banding, structure, and phase behavior in wormlike micellar solutions
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DOI：
10.1039/b900948e
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发表时间：
2009-10
期刊：
影响因子：
3.4
通讯作者：
M. Helgeson;M. Reichert;Y. T. Hu;N. Wagner
中科院分区：
文献类型：
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作者：
M. Helgeson;M. Reichert;Y. T. Hu;N. Wagner
研究了浓阳离子虫状胶束表面活性剂（十六烷基三甲基溴化铵）在各向同性向列相（I-N）转变附近的流变行为，并将其作为组分和温度的函数来确定剪切带、流体微观结构和底层平衡相行为之间的关系。传统流变学、测速法和空间分辨流-小角中子散射相结合，可以详细探索剪切带和非剪切带解决方案之间的差异。Giesekus本构模型可以很好地描述各向同性WLM溶液的剪切流变特性，该模型通过阻力各向异性耦合参数对带状和非带状虫状胶束流体进行了定量区分。这种各向异性参数与描述到平衡I-N跃迁的相对距离的序参数相关。将这些信息与剪切带的临界剪切速率的测量相结合，可以根据Weissenberg数和组成顺序参数构建剪切带流体的非平衡状态图。
The rheological behavior of concentrated cationic wormlike micellar surfactant solutions (cetyltrimethylammonium bromide) near the isotropic–nematic (I–N) transition is studied as a function of composition and temperature to determine the relationship between shear banding, fluid microstructure and underlying equilibrium phase behavior. The combination of conventional rheometry, velocimetry, and spatially-resolved flow-small angle neutron scattering allows detailed exploration of the differences between shear banding and non-shear banding solutions. The shear rheology of isotropic WLM solutions are shown to be well-described by the Giesekus constitutive model, which provides a quantitative discrimination between banding and non-banding wormlike micellar fluids through the drag anisotropy coupling parameter. This anisotropy parameter is shown to correlate with the order parameter describing the relative distance to the equilibrium I–N transition. Combining this information with measurements of the critical shear rates for shear banding allows the construction of a non-equilibrium state diagram for the shear banding fluid in terms of the Weissenberg number and the compositional order parameter.