Nanopatterning of Liquid–Liquid Interfaces by Mikto-Grafted Molecular Brush Polymers

Heterografted molecular brush polymers are promising effective stabilizers for oil/water interfaces. These polymers possess highly customizable architectural parameters, such as backbone and side chain lengths, as well as the chemical compatibility of side chains with different solvents. In this work, extensive molecular simulations were performed to investigate how heterografted molecular brushes with hydrophilic and amphiphobic side chains organize at planar and spherical liquid–liquid interfaces. Different polymer architectural parameters were varied, as well as polymer surface concentration, to elucidate the dependence of interfacial thermodynamic properties and molecular organization on these parameters. It was found that the organization of these polymers at the water–oil interface is significantly influenced by the asymmetry in side chain lengths: Polymers with short amphiphobic side chains and long hydrophilic side chains form stable lattices with local hexagonal symmetry at intermediate to high surface concentrations. In contrast, polymers with symmetric side chain lengths form lattices with local hexagonal symmetry at intermediate concentrations and in-plane lamellar structures at high concentrations. This behavior was also observed in spherical oil-in-water and water-in-oil droplets, affording emulsion droplets with nanopatterned interfaces. The backbone length plays a minor role on the interfacial tension reduction, whereas side chain length asymmetry is more critical and the combination of short backbones and asymmetric side chains is more effective at reducing interfacial tension. In addition, several single-chain descriptors were computed to correlate molecular structure with surface concentration and interfacial thermodynamics.