Swelling of model polymer networks with different cross-link densities: a computer simulation study

Area of Science:

• Polymer Science
• Computational Chemistry
• Materials Science

Background:

• Understanding polymer network swelling is crucial for applications like drug delivery and soft robotics.
• Molecular dynamics simulations offer a powerful tool to probe complex swelling behaviors at the molecular level.

Purpose of the Study:

• To investigate the equilibrium swelling ratio and solvent diffusion in model polymer networks.
• To explore the influence of cross-link density, temperature, and pressure on network swelling.
• To compare simulation results with Flory-Huggins-type theory.

Main Methods:

• Molecular dynamics simulations were employed using two coupled boxes: one for the polymer network and solvent, and another for the solvent only.
• Solvent chemical potential difference, calculated using Widom test particle method and Rosenbluth sampling, controlled particle transfer.
• Equilibrium swelling ratio and solvent diffusion coefficients were computed under various subcritical and supercritical conditions.

Main Results:

• The equilibrium swelling ratio and solvent diffusion coefficient were determined as functions of network cross-link density.
• Results were analyzed across a wide range of temperatures and pressures, including subcritical and supercritical conditions.
• Simulated swelling behavior demonstrated qualitative agreement with Flory-Huggins-type theory.

Conclusions:

• Cross-link density, temperature, and pressure significantly influence polymer network swelling and solvent diffusion.
• Molecular dynamics simulations provide valuable insights into polymer network behavior.
• The study validates theoretical models for polymer network swelling under diverse conditions.