(692c) How Does the Crystallization Phase Behavior of an Oligomer Melt Depend on Molecular Parameters?

Hundreds of millions of tons of semi-crystalline polymers are produced each year, including commodity and engineering plastics and specialized polymers such as semiconductors. Despite their ubiquity and technological importance, the molecular mechanisms of polymer crystallization remain controversial. One important aspect that remains a subject of debate is the role that the low-temperature phase behavior plays on the process of nucleation. Accordingly, we have developed advanced sampling Monte Carlo approaches including the Wang-Landau (WL) and Expanded Ensemble Density of States (EXEDOS) methods to compute phase diagrams and free energy landscapes (FELs) relevant for crystallization of a melt of short chains. We find evidence that crystal nucleation is quite sensitive to chain flexibility, but rather insensitive to other molecular parameters. While these findings are presently limited to oligomers, if they generalize to a broader class of molecules, they will have significant implications for the long-standing debate over multistep crystallization processes and even perhaps for the ability to categorize different polymers into “universality classes” with regards to crystallization.