Flow-Induced Structured Phase in Nonionic Micellar Solutions

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• 作者：Joshua J. Cardiel ; Lige Tonggu ; Pablo de la Iglesia ; Ya Zhao ; Danilo C. Pozzo ; Liguo Wang ; Amy Q. Shen
• 刊名：Langmuir
• 出版年：2013
• 出版时间：December 17, 2013
• 年：2013
• 卷：29
• 期：50
• 页码：15485-15495
• 全文大小：584K
• 年卷期：v.29,no.50(December 17, 2013)
• ISSN：1520-5827

文摘

In this work, we consider the flow of a nonionic micellar solution (precursor) through an array of microposts, with focus on its microstructural and rheological evolution. The precursor contains polyoxyethylene(20) sorbitan monooleate (Tween-80) and cosurfactant monolaurin (ML). An irreversible flow-induced structured phase (NI-FISP) emerges after the nonionic precursor flows through the hexagonal micropost arrays, when subjected to strain rates 10⁴ s^鈥? and strain 10³. NI-FISP consists of close-looped micellar bundles and multiconnected micellar networks as evidenced by transmission electron microscopy (TEM) and cryo-electron microscopy (cryo-EM). We also conduct small-angle neutron scattering (SANS) measurements in both precursor and NI-FISP to illustrate the structural transition. We propose a potential mechanism for the NI-FISP formation that relies on the micropost arrays and the flow kinematics in the microdevice to induce entropic fluctuations in the micellar solution. Finally, we show that the rheological variation from a viscous precursor solution to a viscoelastic micellar structured phase is associated with the structural evolution from the precursor to NI-FISP.