Exploiting Polymer Theory to Simulate the Rheology of Micellar Solutions and Polymer Glasses

Abstract

Exhibiting different rheological (viscoelastic) behaviors, micellar solutions and polymeric glasses are at the center of many applications. For micellar solutions, I have developed a mesoscopic simulation model, drawing from concepts developed for entangled polymer melts, to account for linear rheology of different micelle structures (linear and branched micelles). Through a “pointer” algorithm I developed, this new model tracks boundaries between relaxed and unrelaxed parts of micelles that are diffusing in entanglement tubes, and uses polymer-like mechanisms along with intermicellar reactions (breakage and reformation) to compute rheology, which allows, for the first time, not only quantitative prediction of flow behaviors but also estimation of important micelle properties from rheological measurement with much greater accuracy than ever before. For polymeric glasses, by treating the short glassy segments as “solvent” for the slow-relaxing polymeric part, a hybrid model has been developed that combines a constitutive model of the glassy solvent with Brownian dynamics simulations of polymers, whose relaxation is coupled to the glassy dynamics through the drag coefficient. This hybrid model successfully captures numerous behaviors of polymeric glass (yielding, strain hardening, recovery, physical aging, and flow rejuvenation) under various types of deformations as well as the effects of polymer pre-orientation, whose results prove to be consistent with observations from both experiments and molecular level simulations.