Seminar

Since its first perception almost three decades ago, it is widely accepted that geometrical confinement may alter the glass transition temperature (Tg) in thin glassy polymer films with respect to bulk, as a result of perturbations induced by interfacial interactions at the substrate and the presence of a free surface. The effect of competing interfaces further led to several important findings, such as, those on gradient in Tg, viscosity, shear mobility, and structural relaxation. It is also well known preparation induced non-equilibrium imposed in polymer chain conformation (polymer chain entanglement) affects its mechanorheological properties and stability. Such understanding has deep intellectual interest from the standpoint to understand the glass transition of polymers under geometrical confinement, especially structures where polymers have nanoscale interface shared with non-polymeric substance.

Throughout the discussion I will show how simple time-resolved dynamics of mechanical instabilities in polymer thin films when followed through microscopic techniques can deliver important understanding on the nanorheology of thin glassy polymer films. I will emphasize pertinent questions that can ask suprising questions on the decoupled glassy dynamics in thin polymer films around two major areas we developed. I. Noncontact Capillary Nanoshearing ll. Molecular recoiling stress and hole growth dynamics.