Reconfiguration and Reorganization of Bottlebrush Polymer Surfactants

Bottlebrush random copolymers (BRCPs), having randomly distributed hydrophilic and hydrophobic side chains, are shown to reconfigure into hydrophilic-rich and hydrophobic-rich conformations at liquid-liquid interfaces to reduce interfacial energy. Both the degree of polymerization (NBB ) and extent of grafting in these BRCPs were found to impact surface coverage and assembly kinetics. The time-dependence of the interfacial tension is described as the sum of two exponential relaxation functions characterizing BRCP diffusion, interfacial adsorption, and reorganization. Interfacial tension (γ) and fluorescence recovery after photobleaching (FRAP) results showed that higher molecular weight BRCPs require longer time to adsorb to the water-oil interface, but less time for interfacial reorganization. Overall, this work describes fundamental principles of BRCP assembly at liquid-liquid interfaces, with implications pertaining to polymer design with enhanced understanding of emulsification, adhesion, and related properties in fluids and at interfaces.