Foam film stratification studies probe intermicellar interactions
Foam film stratification studies probe intermicellar interactions
复制标题
DOI：
10.1073/pnas.2024805118
复制
发表时间：
2021-06
期刊：
影响因子：
--
通讯作者：
C. Ochoa;Shang Gao;Samanvaya Srivastava;Vivek Sharma
中科院分区：
文献类型：
--
作者：
C. Ochoa;Shang Gao;Samanvaya Srivastava;Vivek Sharma
胶束间距离和相互作用的定量表征需要使用定制的，昂贵的技术，如小角度X射线或中子散射，表面力装置，和原子力显微镜。在这里，我们利用干涉数字成像光学显微镜（IDIOM）的协议来表征纳米级的地形变化和分层胶束泡沫膜逐步变薄。我们发现，步长等于胶束间的距离使用小角X-射线散射实验散装解决方案。我们直接比较这些长度尺度明确支持流体动力学机制分层的基础上薄膜方程和分离压力计算使用液态理论。我们设想，我们的贡献将激励科学家探索泡沫膜的研究，作为表征纳米级胶体相互作用和力量的简单而有效的方法。超薄泡沫膜含有超分子结构，如本体胶束和吸附的表面活性剂在液体-空气界面通过分层进行排水。在固定的表面活性剂浓度下，分层胶束膜的平均膜厚度的逐步减小产生特征步长，该特征步长还描述了共存的厚薄平坦区域之间的量化厚度差。尽管许多已发表的研究声称，步长等于胶束间的距离，获得使用散射从散装解决方案，我们发现没有报告的两个长度尺度之间的直接比较。已经确定的是，步长与表面活性剂浓度的立方根成反比，但不能通过将胶束尺寸与德拜长度相加来估计，因为德拜长度与表面活性剂浓度的平方根成反比。在这方面的贡献，我们对比的步长从分析纳米级的厚度变化和过渡分层泡沫膜使用干涉数字成像光学显微镜（IDIOM）协议，我们开发的，与使用小角度X-射线散射得到的胶束间距离。我们发现，分层驱动的约束诱导分层的胶束内的液体-空气界面的泡沫膜提供了一个敏感的探针的非DLVO（Derjaguin-Landau-Verwey-Overbeek）超分子振荡结构力和胶束相互作用。
Significance Quantitative characterization of intermicellar distances and interactions requires the use of bespoke, expensive techniques like small angle X-ray or neutron scattering, surface force apparatus, and atomic force microscopy. Here, we utilize Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols to characterize nanoscopic topographical changes and stepwise thinning in stratifying micellar foam films. We find that the step size equals the intermicellar distance obtained using small-angle X-ray scattering experiments on bulk solutions. Our direct comparison of these length-scales unequivocally supports the hydrodynamic mechanism for stratification based on thin-film equation and disjoining pressure computed using liquid-state theory. We envision that our contributions will inspire scientists to explore foam film studies as simple but effective methods for characterizing nanoscopic colloidal interactions and forces. Ultrathin foam films containing supramolecular structures like micelles in bulk and adsorbed surfactant at the liquid–air interface undergo drainage via stratification. At a fixed surfactant concentration, the stepwise decrease in the average film thickness of a stratifying micellar film yields a characteristic step size that also describes the quantized thickness difference between coexisting thick–thin flat regions. Even though many published studies claim that step size equals intermicellar distance obtained using scattering from bulk solutions, we found no reports of a direct comparison between the two length scales. It is well established that step size is inversely proportional to the cubic root of surfactant concentration but cannot be estimated by adding micelle size to Debye length, as the latter is inversely proportional to the square root of surfactant concentration. In this contribution, we contrast the step size obtained from analysis of nanoscopic thickness variations and transitions in stratifying foam films using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols, that we developed, with the intermicellar distance obtained using small-angle X-ray scattering. We find that stratification driven by the confinement-induced layering of micelles within the liquid–air interfaces of a foam film provides a sensitive probe of non-DLVO (Derjaguin–Landau–Verwey–Overbeek) supramolecular oscillatory structural forces and micellar interactions.