Heterogeneous nucleation of an n-alkane on graphene-like materials

Abstract

Nucleating agents are materials that enhance crystallization through their role in heterogeneous nucleation. They are frequently used to control kinetics and morphology in polymer crystallization. However, selection and design of nucleating agents is hindered by a lack of detailed, atomistic level information about the relationship between physicochemical properties and heterogeneous nucleation activity. We examined heterogeneous nucleation of n-pentacontane – a model surrogate for polyethylene – induced by graphene, and the family of 2D hexagonally coordinated nanoplatelet materials to which it belongs, using molecular dynamics simulation. High throughput computational screening was performed by systematic variation of the parameters that define the 2D nanoplatelet. Nucleation activity is characterized by induction time. These computations confirm the utility of graphene as a nucleating agent for n-pentacontane and, by extension, polyethylene. We identify a set of heuristics for the design of efficient nucleating agents. These include: epitaxial matching, material compatibility as measured by adhesive interactions, and optimal rigidity. We also observed a three-fold degeneracy in the orientation of epitaxial matches between the nucleating agent and the crystallizing organic, which increased the induction time. This study advances the prospect of high-throughput computation to build a “materials genome” of nucleating agents for polymers.