(589a) Perfect Mixing of Immiscible Macromolecules At Fluid Interfaces

Mixing of chemically different substances is an emblematic problem confronted by the health care, nutrition, and materials industries. This problem becomes particularly challenging when mixing large species, such as macromolecules and colloidal particles that exhibit particularly low increase of specific translational entropy upon mixing - the main driving force of mixing. One of the strategies for enhancement of mixing propensity is to modify the interaction energy by introducing a net attraction between chemically dissimilar molecules. The implications of this strategy can be observed in many natural systems, e.g., salts, stereoregular polymers, and lock-and-key assemblies. In all these systems, the mixing largely relies on a specific nature of chemical structures and/or physical shapes of objects being mixed. We propose a different strategy which requires neither chemical nor shape complementarity. The “perfect” mixing (intercalation) is achieved at fluid interfaces due to steric repulsion between brush-like macromolecules. The net repulsion is caused by the decrease of conformational entropy of polymeric branches in densely packed monolayers, which effectively creates evenly spaced potential wells attracting species of various chemistries and shapes. This strategy was successfully applied to mixing of polymer bottlebrushes, stars, and linear chains possessing hydrophilic, hydrophobic, and lypophobic chemical compositions. Interfacial mixing has vital implications in biological systems and also offers a new approach to surface patterning of thin films on sub-100 nm length scales.