Multiscale dynamic Monte Carlo/continuum model of drying and nonideal polycondensation in sol-gel silica films

The process of forming sol-gel silica thin films involves multiple length and time scales ranging from molecular to macroscopic, and it is challenging to fully model because the polymerization is nonideal. A multiscale model is described to link macroscopic flow and drying (controlled by process parameters) to film microstructure (which dictates the properties of the films). In this modeling strategy, dynamic Monte Carlo (DMC) polymerization simulations are coupled to a continuum model of drying. The entire DMC simulation is treated as a particle of sol whose position and composition are tracked using a diffusion/evaporation finite difference method. By simulating swarms of particles starting from different positions in the film, the multiscale model predicts different drying/gelation phenomena, and predicts the occurrence of gradients of concentration and gelation in the films which can lead to the formation of a gel skin near the top surface of the film.