Author ORCID Identifier
https://orcid.org/0000-0001-7744-9226
Date of Award
Spring 6-15-2025
Document Type
Thesis (Ph.D.)
Department or Program
Chemistry
First Advisor
Wenlin Zhang
Second Advisor
Dale F. Mierke
Third Advisor
Dean E. Wilcox
Abstract
Semicrystalline polymers are used in various applications, from commodity plastics to high-performance materials. Their properties are strongly influenced by crystallization behavior. However, the fundamental mechanisms governing polymer crystallization remain incompletely understood, particularly due to the complex kinetic constraints arising from chain connectivity.
This dissertation investigates the role of chain entanglements in polymer crystallization through molecular dynamics (MD) simulations. We examine both nucleation and growth processes in polymer melts. At high supercooling, our findings indicate that nucleation is predominantly a local event, sensitive to factors such as local segmental dynamics, and largely unaffected by long-range topological constraints such as entanglements.
In contrast, during crystal growth, entanglements impose significant kinetic constraints that limit lamellar thickening and contribute to the development of semicrystalline morphology. We quantified the entanglement evolution during polyethylene crystallization and found that crystal growth requires disentanglement at the growth front. However, as crystallization proceeds, increasing numbers of entanglements become trapped near the crystal surface, which impedes further crystal growth.
To overcome the spatial and temporal limitations of MD simulations, we also developed a phase field model tailored for polymer crystallization. The model incorporates key physical features such as lamellar thickness constraints to capture the effects of chain entanglements. Informed by both simulation and experimental parameters, the model successfully reproduces characteristic features in polymer crystallization.
Altogether, this dissertation provides new understanding of how entanglement and local dynamics govern polymer crystallization, and offers a mesoscale model for predicting crystalline morphology in semicrystalline polymer systems.
Original Citation
Zou, Lingyi, and Wenlin Zhang. "Molecular dynamics simulations of the effects of entanglement on polymer crystal nucleation." Macromolecules 55.12 (2022): 4899-4906.
Zou, Lingyi, and Wenlin Zhang. "Effects of entanglement on polymer crystal growth and intercrystalline phase formation." Macromolecules 57.9 (2024): 4410-4420.
Zou, Lingyi, and Wenlin Zhang. "Roles of Interfaces in Crystallization in Freestanding and Bilayer Polymer Films." Macromolecules 58.7 (2025): 3589-3594.
Recommended Citation
Zou, Lingyi, "Multi-scale Simulations Reveal the Effects of Entanglement on Polymer Crystallization" (2025). Dartmouth College Ph.D Dissertations. 353.
https://digitalcommons.dartmouth.edu/dissertations/353
