title: Nanoscopic Terraces, Mesas, and Ridges in Freely Standing Thin Films Sculpted by Supramolecular Oscillatory Surface Forces.
abstract: Freely standing thin liquid films containing supramolecular structures including micelles, nanoparticles, polyelectrolyte-surfactant complexes, and smectic liquid crystals undergo drainage via stratification. The layer-by-layer removal of these supramolecular structures manifests as stepwise thinning over time and a coexistence of domains and nanostructures of discretely different thickness. The layering of supramolecular structures in confined thin films contributes additional non-DLVO, supramolecular oscillatory surface forces to disjoining pressure, thus influencing both drainage kinetics and stability of thin films. Understanding and characterizing the spontaneous creation and evolution of nanoscopic topography of stratifying, freely standing thin liquid films have been long-standing challenges due to the absence of experimental techniques with the requisite spatial (thickness <10 nm) and temporal resolution (<1 ms). Using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols developed herein, we visualize and characterize size, shape, and evolution kinetics of nanoscopic mesas, terraces, and ridges. The exquisite thickness maps created using IDIOM protocols provide much needed and unprecedented insights into the role of supramolecular oscillatory surface forces in driving growth of such nanostructures as well as in controlling properties and stability of freely standing thin films and, more generally, of colloidal dispersions like foams.
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Yiran
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Subinuer
authors.initials: S
authors.lastname: Yilixiati
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Collin
authors.initials: C
authors.lastname: Pearsall
authors.affiliation: Department of Chemical Engineering, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Vivek
authors.initials: V
authors.lastname: Sharma
keywords: DLVO theory; imaging; micelles; optical microscopy; surface forces; thin film