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Multiscale Assembly of Polymer Materials away from Equilibrium

Douglas Tree from Brigham Young University

Production methods for many polymers do not lead to materials at equilibrium, but instead give process-history dependent microstructures and properties. While there are sophisticated theories and simulation methods for describing equilibrium polymer systems that span molecular to continuum length-scales, our understanding of systems away from equlibrium are more primitive. I will focus on two different industrially relevant examples: polymers that crystallize and polymers that precipitate out of solution. In the first case, despite the prevalence of semicrystalline polymers, the fundamental mechanisms of crystallization of a polymer melt are still controversial. In particular, there are several competing theories of nucleation, with increasing evidence that nematic ordering plays an important (and previously unappreciated) role. I will discuss our recent work characterizing the free energy landscape (FEL) of oligomer crystal nucleation using advanced Monte Carlo methods and its implication in this ongoing debate. In the second example, I will discuss some our work using field-based simulation methods to understand the process of nonsolvent induced phase separation (NIPS), widely used for the production of polymer membranes and porous micro/nanoparticles. Specifically, I will discuss our development of a multicomponent phase-field model that is able to capture the relevant phase separation, mass transfer, and hydrodynamic processes that lead to microstructure formation in these systems.