Molecular dynamics simulation for shape change of water-in-oil droplets

Abstract

We performed molecular dynamics (MD) simulations of water-in-oil droplet shape transformations induced by the addition of polymer chains. In a prior experiment, transformations of spherical droplets to rod-like, worm-like and network-like droplets were observed. In our previous study, we reproduced rod-like droplets via coarse-grained MD simulations, and the mechanism for the droplet shape change was elucidated by considering the contact area between the chains and the surfactant head groups. However, in that simulation model, we could not reproduce the worm-like and network-like droplets. In this study, we improved the simulation model. For a small number of chains, several spherical droplets were obtained. As the number of chains increased, the spherical droplets were transformed to rod-like, worm-like and networklike shapes by coalescence of the droplets. The calculated and experimental results agreed well, and we verified that the mechanism for the droplet shape transformations observed in the present simulations could be explained by the mechanism suggested in the previous study.