"Three dimensionally ordered array of air bubbles in a polymer film: It is
not all hot air!"
Mohan Srinivasarao
School of Textile and Fiber Engineering
Georgia Institute of Technology
Abstract
Systems driven far from equilibrium have a remarkable tendency to produce
very ordered structures. Such ordered structures have been observed in many
a situation where the material, for example a liquid crystal in its nematic
phase, subjected to an external perturbing field, responds to this
perturbation by creating ordered periodic structures. We report on the
formation of a three dimensionally ordered array of air bubbles in a polymer
film with a monodisperse pore size. Dilute solutions of a simple, coil-like
polymer, is cast on a glass slide in the presence of moist air flowing
across the surface. Such films consist of multilayers of hexagonally packed
array of spherical air bubbles, whose dimensions can be controlled quite
easily, simply by changing the velocity of the airflow across the surface.
The structures are formed by a templating mechanism unlike most published in
literature, and uses the phenomenon of evaporative cooling, leading to an
ordered array of breath figures, which are preserved in the final solid
polymer film. Our preliminary work has identified the mechanism to be that
of condensation of moisture on the polymer surface resulting from a cooling
due to evaporation of the volatile solvent.
Elizabeth K. Mann