Fast Diffusion-Limited Lyotropic Phase Transitions Studied in Situ Using Continuous Flow Microfluidics/Microfocus-SAXS

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• 作者：Sebastian With ; Martin Trebbin ; Christian B. A. Bartz ; Christian Neuber ; Martin Dulle ; Shun Yu ; Stephan V. Roth ; Hans-Werner Schmidt ; Stephan F枚rster
• 刊名：Langmuir
• 出版年：2014
• 出版时间：October 28, 2014
• 年：2014
• 卷：30
• 期：42
• 页码：12494-12502
• 全文大小：536K
• ISSN：1520-5827

文摘

Fast concentration-induced diffusion-limited lyotropic phase transitions can be studied in situ with millisecond time resolution using continuous flow microfluidics in combination with microfocus small-angle X-ray scattering. The method was applied to follow a classical self-assembly sequence where amphiphiles assemble into micelles, which subsequently assemble into an ordered lattice via a disorder/order transition. As a model system we selected the self-assembly of an amphiphilic block copolymer induced by the addition of a nonsolvent. Using microchannel hydrodynamic flow-focusing, large concentration gradients can be generated, leading to a deep quench from the miscible to the microphase-separated state. Within milliseconds the block copolymers assembly via a spinodal microphase separation into micelles, followed by a disorder/order transition into an FCC liquid-crystalline phase with late-stage domain growth and shear-induced domain orientation into a mesocrystal. A comparison with a slow macroscopic near-equilibrium kinetic experiment shows that the fast structural transitions follow a direct pathway to the equilibrium structure without the trapping of metastable states.