Solubility of selected polymers in cyclohexane: comparison between Flory-Huggins interaction parameters calculated...

Area of Science:

• Computational Chemistry
• Polymer Science
• Materials Science

Background:

• Accurate prediction of polymer solubility is crucial for practical applications.
• The Flory-Huggins interaction parameter (χ) is a key metric for solubility prediction.
• Molecular dynamics (MD) simulations are powerful tools for calculating χ.

Purpose of the Study:

• To evaluate three MD simulation strategies for calculating the Flory-Huggins interaction parameter (χ).
• To compare the accuracy and computational efficiency of different methods for determining polymer solubility.
• To analyze polymer conformational changes in solution using MD simulations.

Main Methods:

• Calculated χ using three MD simulation strategies: Hildebrand solubility parameters, enthalpy of solvation, and Gibbs free energy of solvation.
• Studied binary solutions of various hydrophobic and hydrophilic polymers (e.g., polystyrene, polyisobutylene, PEO, polyacrylamide) in cyclohexane.
• Performed conformational analysis, including radius of gyration (Rg) and solvent accessible surface area (SASA).

Main Results:

• The solubility parameter approach predicted trends but deviated significantly from experimental values.
• Enthalpy of solvation yielded the most accurate χ values with reasonable computational demand, especially for hydrocarbon polymers.
• Gibbs free energy of solvation was computationally intensive and overestimated χ for non-polar polymers, without significant accuracy improvement over enthalpy.

Conclusions:

• The enthalpy of solvation method is the most effective MD strategy for accurate and efficient calculation of χ.
• Polymer conformational changes (collapse) were observed in cyclohexane, with polar polymers showing more pronounced effects.
• The choice of MD simulation strategy significantly impacts the accuracy and resource requirements for determining polymer solubility.