Modeling Solution Drying by Moving a Liquid-Vapor Interface: Method and Applications

TL;DR

This paper introduces a moving liquid-vapor interface simulation method for drying processes in soft matter solutions, demonstrating its effectiveness across various systems and morphologies, and discussing its limitations.

Contribution

The paper presents a novel implicit solvent model with a moving interface for simulating drying, applicable to diverse solution films and droplets with complex particle behaviors.

Findings

Polymer-on-top stratification observed in simulations.

Core-shell nanoparticle clusters formed at fast evaporation.

Various polymer particle morphologies achieved through controlled drying.

Abstract

A method of simulating the drying process of a soft matter solution with an implicit solvent model by moving the liquid-vapor interface is applied to various solution films and droplets. For a solution of a polymer and nanoparticles, we observe "polymer-on-top" stratification, similar to that found previously with an explicit solvent model. Furthermore, "polymer-on-top" is found even when the nanoparticle size is smaller than the radius of gyration of the polymer chains. For a suspension droplet of a bidisperse mixture of nanoparticles, we show that core-shell clusters of nanoparticles can be obtained via the "small-on-outside" stratification mechanism at fast evaporation rates. "Large-on-outside" stratification and uniform particle distribution are also observed when the evaporation rate is reduced. Polymeric particles with various morphologies, including Janus spheres, core-shell particles, and patchy particles, are produced from drying droplets of polymer solutions by combining fast evaporation with a controlled interaction between the polymers and the liquid-vapor interface. Our results validate the applicability of the moving interface method to a wide range of drying systems. The limitations of the method are pointed out and cautions are provided to potential practitioners on cases where the method might fail.