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Updated: Mar 3, 2026
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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
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Effects of Orientational and Conformational Ordering on Isotactic Polypropylene Crystallization
Anderson D S Duraes1, Wenlin Zhang1
1Department of Chemistry, Dartmouth College, 41 College Street, Hanover, New Hampshire 03755, United States.
Macromolecules
|March 2, 2026
Summary
Flows alone do not induce crystallization in isotactic polypropylene (iPP) oligomers. Conformational ordering, not just chain alignment, is crucial for iPP nucleation and crystallization in simulations.
Area of Science:
- Polymer Science
- Materials Science
- Computational Chemistry
Background:
- Crystallization of isotactic polypropylene (iPP) is critical for its material properties.
- Understanding the role of external flows in polymer crystallization is key for processing control.
- Previous studies have explored flow effects, but the interplay between chain conformation and orientation remains debated.
Purpose of the Study:
- To investigate the impact of shear and extensional flows on iPP oligomer crystallization using atomistic simulations.
- To differentiate the effects of orientational alignment versus conformational ordering on nucleation.
- To determine the conditions necessary for flow-induced crystallization in iPP.
Main Methods:
- Atomistic nonequilibrium molecular dynamics (NEMD) simulations.
- Simulations of homogeneous shear and uniaxial extensional flows.
- Analysis of chain alignment, conformational order, and nucleation kinetics.
- Application of classical nucleation theory.
Main Results:
- Extensional flows induced stronger, molecular-weight-dependent alignment than shear flows.
- Neither flow type induced helical conformational order in iPP.
- Flow-induced orientational order alone was insufficient for rapid iPP nucleation without maintained stress.
- Inducing helical order via dihedral restraints led to rapid crystallization at elevated temperatures.
Conclusions:
- Conformational ordering is essential for efficient iPP nucleation and crystallization, more so than orientational alignment alone.
- Flow-induced crystallization requires both conformational ordering and sufficient stress.
- Simulation results align with experimental observations of iPP melting behavior.
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