Time Matters: Predicting and Tailoring the Nonequilibrium Behavior of Polymers
ABSTRACT :
Performance and properties of materials may strongly depend on processing conditions. This is particularly so for polymers, which often have relaxation times much longer than the processing times and therefore may adopt preparation dependent non-equilibrated molecular conformations that potentially cause novel properties. However, so far it was not possible to predictably and quantitatively relate processing steps and the resulting behavior of polymer films. In this talk, I will highlight the results of my recent experiments demonstrating that the behavior of polymer films can be tuned by controlled preparation pathways, defined through a dimensionless parameter p that relates the processing time with the characteristic relaxation time of polymers. We revealed scaling relations between p and the amount of preparation-induced residual stresses, corresponding relaxation times, and the probability of film rupture. Using such relations, we have shown that the application properties (viscoelastic properties and crystallization kinetics) of the polymer films of same thickness, but different p, can be tailored by orders of magnitude. Additionally, I will briefly discuss the future experimental prospects, especially, aiming at exploiting processing induced non-equilibrium states of polymers for controlling their properties.