Simulation of Dissolution Process of Hydrophobic Coated Core- Shell Particles at Interface of Two Immiscible Fluids

The main purpose of this paper is modeling and simulation of in-situ releasing of the nano size polymeric core and shell particle in the interface of two immiscible fluids. When these particles reach at the organic-aqueous interface the hydrophobic coating layer starts dissolving into the organic phase. After removing of the coat, the main inside polymer which is not soluble in the organic phase starts to diffuse back into the aqueous phase and increase the viscosity of the aqueous phase. In this paper, the governing equations of the process are obtained and numerically solved. The coating dissolution is considered as spherical diffusion followed by polymer chain disentanglement through a diffusion boundary layer. Moreover, a swellable-chain disentanglement model and concentration-dependent diffusion coefficient is considered for inside polymer dissolution into the aqueous phase which leads to a nonlinear partial differential equation with two moving boundries at both sides. Using finite difference scheme, the governing equation are numerically solved by defining some dimensionless parameters for the main parameters as well as the moving boundaries. Finally, a sensitivity analysis is performed for investigating the impact of different parameters affecting the dissolution process.