Modeling size controlled nanoparticle precipitation with the co-solvency method by spinodal decomposition

Area of Science:

• Polymer science
• Materials science
• Physical chemistry

Background:

• The co-solvency method enables controlled preparation of nanoparticles, such as polymersomes.
• Nanoparticle size is dictated by the rate of co-solvent addition during polymer precipitation.

Purpose of the Study:

• To model the polymer precipitation process during co-solvency using a time-dependent Flory-Huggins interaction parameter.
• To investigate the relationship between nanoparticle size and the rate of solvent quality change during spinodal decomposition.

Main Methods:

• Utilized the Cahn-Hilliard equation coupled with a Flory-Huggins free energy model.
• Applied a time-dependent Flory-Huggins interaction parameter to simulate changing solvent quality.
• Performed numerical simulations and perturbation analysis.

Main Results:

• Identified a characteristic size (R) for polymer aggregates during spinodal decomposition.
• Predicted a power law dependence of nanoparticle size on the rate of solvent quality change: R∼s(-⅙).
• Demonstrated agreement between model predictions and experimental/simulation data.

Conclusions:

• Nanoparticle size in co-solvency precipitation is predominantly determined during the initial spinodal decomposition phase.
• The R∼s(-⅙) power law provides a theoretical basis for controlling nanoparticle size.
• The Cahn-Hilliard/Flory-Huggins model effectively describes polymer precipitation dynamics in co-solvency.