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Characterization of polyethylene crystallization from an oriented melt by molecular dynamics simulation
Min Jae Ko1, Numan Waheed, Marc S Lavine
1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
The Journal of Chemical Physics
|July 30, 2004
Summary
Molecular dynamics simulations reveal polyethylene crystallization, showing crystal nucleation, lamellar growth, and thickening. The findings align with experimental data on lamellar thickness and interfacial energy effects.
Area of Science:
- Materials Science
- Polymer Science
- Computational Chemistry
Background:
- Understanding polymer crystallization is crucial for material properties.
- Molecular dynamics offers a powerful tool to probe nanoscale processes.
Purpose of the Study:
- To characterize the crystallization process of polyethylene using molecular dynamics.
- To investigate nucleation, growth, and thickening mechanisms at the molecular level.
Main Methods:
- Utilized molecular dynamics simulations with a united atom model for polyethylene.
- Simulated crystallization by orienting a melt via uniaxial deformation and quenching.
- Monitored crystallinity using molecular-based order parameters for density, energy, and orientation.
Main Results:
- Observed clear hallmarks of crystal nucleation and growth at 325–375 K.
- Identified multiple nucleation events, lamellar growth, and lamellar thickening.
- Noted competition between nucleation, chain extension, and conformational relaxation rates.
- Found temperature dependence of lamellar thickness consistent with experimental data.
- Observed tilted chain lamellae formation at higher temperatures, influenced by interfacial energy.
Conclusions:
- Molecular dynamics simulations effectively capture polyethylene crystallization dynamics.
- The study elucidates the interplay of kinetic factors governing crystal morphology.
- Results provide insights into the molecular origins of lamellar structure and interfacial phenomena.