Structure and Organization of Amphiphilic Mikto-Grafted Molecular Brushes at Oil/Water Interfaces: A Dissipative Particle Dynamics Study.

It has been recently found that amphiphilic molecular bottlebrush polymers are able to stabilize oil/water interfaces at extremely low concentrations, creating a pathway to develop stable oil-in-water emulsions for applications in cosmetics, oil, food, and pharmaceutical industries. An understanding of the effect of the different molecular parameters on the structure and organization of these polymers at oil/water interfaces is an important step towards the molecular engineering of advanced bottlebrush-stabilized emulsions. Amphiphilic mikto-grafted molecular brushes possess tunable architectural parameters, including the backbone length, N_bb, and the lengths of the hydrophilic and hydrophobic sidechains, N_A and N_B, respectively. All of these are expected to have a considerable effect on the conformation of these bottlebrushes at the oil/water interface. In this work, we have performed extensive numerical simulations using Dissipative Particle Dynamics to investigate the role of side chain size-asymmetry and backbone molecular weight on the structure and organization of bottlebrush polymers at planar oil/water interfaces. The effect of the polymer concentration was also investigated. To characterize polymer structure, we computed the gyration tensor, G_M, which was used to calculate the radius of gyration, R_g, the relative shape anisotropy parameter, A₃ and the asphericity, b; end-to-end distances of sidechains and backbone were also computed. In addition, an orientational order parameter tensor was computed to quantify the organization of the bottlebrushes at the interfaces.