Tandrima Banerjee

Molecular dynamics is very useful for studying the molecular mechanisms of formation and stability of surfactant layers locally on the bubble surface. But it is not possible to model the entire macroscopic aphron.

1. Mesoscale modeling (e.g., Dissipative Particle Dynamics — DPD)

Mesoscopic methods (DPD, Lattice Boltzmann, coarse-grained MD) allow modeling systems of much larger size and time compared to classical MD.

Groups of molecules are described as “coarse-grained” particles;

It is possible to consider the behavior of whole bubbles and their coatings;

Allows tracking the formation and stability of macrofoams, analyzing the stability of aphrons in the presence of surfactants.

Limitations: It is necessary to correctly parameterize the model (determine what properties and interactions the “particles” have that correspond to groups of molecules); less “detailing”, processes at the “cluster” level are visible.

Conclusion:

Mesoscale simulations are the optimal choice for modeling aphrons. This makes it possible to study the formation of macrofoams, the stability of surfactant coatings, the interaction between aphrons, etc.

2. Combined (multiscale) approach

Sometimes multiscale modeling is used:

First, the details of the interactions are studied at the MD level and parameters for mesoscopic models are formed;

Then, DPD or other simulations of larger systems are carried out with these parameters.

SUMMARY:

Molecular dynamics provides data on the structures and processes of surfactants at the bubble interface (at the nanoscale level).

Mesoscale modeling (for example, DPD) allows us to consider entire aphrons, their formation and stability.

Ideally, it is better to combine both approaches!