Temperature-Transferable Coarse-Grained Models for Volumetric Properties of Poly(lactic Acid).

Area of Science:

• Materials Science
• Computational Chemistry
• Polymer Physics

Background:

• Accurate simulation of polymer volumetric properties is crucial for materials design.
• Coarse-grained (CG) models offer computational efficiency for large-scale polymer simulations.
• Polylactide (PLA) is a widely used biodegradable polymer with significant industrial applications.

Purpose of the Study:

• To develop and validate a new coarse-grained model for simulating the volumetric properties of bulk polylactide (PLA).
• To investigate the temperature transferability and accuracy of the developed CG model for predicting thermo-mechanical properties.
• To elucidate the key molecular interactions governing the glass transition in PLA.

Main Methods:

• Development of a new coarse-grained (CG) model where each monomer is represented by a single bead.
• Parametrization of bonded and nonbonded CG potentials against dimer, trimer, tetramer strain energies, and decamer melt densities.
• Molecular dynamics (MD) simulations to reproduce thermal expansion, glass transition, bulk moduli, and conformational properties.
• Rescaling of dihedral and nonbonded potentials to restore glass transition temperature (Tg) and validate volumetric coefficients.

Main Results:

• The developed CG model successfully reproduces the thermal expansion and glass transition of PLA bulk.
• Optimized CG potentials exhibit excellent temperature transferability, validated by the Simha-Boyer relation.
• Dihedral torsions and nonbonded interactions were identified as critical factors for glass transition.
• Simulated bulk moduli and conformational properties align well with reference data across a wide temperature range.

Conclusions:

• The new coarse-grained model provides a reliable and computationally efficient method for simulating PLA volumetric and thermo-mechanical properties.
• The model demonstrates high accuracy and temperature transferability, making it suitable for predicting polymer behavior.
• This multiscale approach holds significant promise for the simulation of various polymers beyond PLA.