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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Crystallization, Nucleation and Self-Assembly

CPP 19.1: Hauptvortrag

Dienstag, 28. März 2023, 09:30–10:00, MER 02

Multiscale Model of Flow-Induced Crystallization in Polymers — David Nicholson, Marat Andreev, Chenmay Gangal, and •Gregory Rutledge — Massachusetts Institute of Technology, Cambridge, MA USA

The structure and properties of a semicrystalline polymer depends sensitively on both its chemico-physical nature and the way it is processed. Flow-induced crystallization (FIC) is one such coupled phenomenon. Models of FIC in polymers must account for the effect of flow on crystallization kinetics, but also the effect of evolving crystallinity on the rheology of the flowing polymer melt. For the first part, atomistic nonequilibrium molecular dynamics (NEMD) simulations are used to characterize the nucleation of a new crystal phase from the polymer melt under homogeneous flow conditions. The kinetics of nucleation are characterized using a mean first-passage time analysis, and a model based on the orientational ordering of Kuhn segments is proposed. For the second part, a variation of the discrete slip-link model (DSM) is used for the rheology of entangled polymer melts that accounts for partial crystallinity through the introduction of crosslinked *bridge* and/or *dangling* segments between developing crystallites, combined with a suspension model to reflect the stiffening associated with a growing crystal phase. This dual-network/suspension model describes well the evolution of both viscoelasticity and crystallinity for a number of linear low-density polyethylenes, and affords a deeper understanding of the essential physics that underlie the coupling between fluid mechanics and phase change.