nn6b01012_si_001.pdf (1.21 MB)
Nanoscopic Terraces, Mesas, and Ridges in Freely Standing Thin Films Sculpted by Supramolecular Oscillatory Surface Forces
journal contribution
posted on 2016-04-08, 00:00 authored by Yiran Zhang, Subinuer Yilixiati, Collin Pearsall, Vivek SharmaFreely 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.