Compression-induced anti-nematic order in glassy and semicrystalline polymers

Area of Science:

• Materials Science
• Polymer Physics
• Computational Materials Science

Background:

• Understanding polymer deformation is crucial for material design.
• Asymmetry in mechanical response (tension vs. compression) is observed but molecular origins are unclear.

Purpose of the Study:

• Investigate the molecular mechanisms behind the asymmetry in polymer deformation under uniaxial tension and compression.
• Determine the influence of polymer chain length on this deformation asymmetry.

Main Methods:

• Utilized molecular dynamics simulations.
• Analyzed intra- and interchain organization during deformation.
• Examined both glassy and semicrystalline polymer structures.

Main Results:

• Deformation asymmetry strongly depends on chain length, peaking at intermediate lengths.
• Tensile deformation leads to chain alignment and nematic order.
• Compressive deformation causes reorganization into planes and anti-nematic order, destroying crystallinity.

Conclusions:

• The molecular structure of polymers under tension and compression is fundamentally different.
• At large strains, the final deformed state depends solely on the deformation mode, not the initial structure.