Amphiphilic Double-Brush Copolymers with a Polyurethane Backbone: A Bespoke Macromolecular Emulsifier for Ionic Liquid-in-Oil Emulsion.

The study on ionic liquid (IL)-based emulsions is very interesting due to the "green" quality and potential wide applications of ILs, whereas the emulsifiers for the formation of IL-based emulsions are extremely limited and mainly centered on low molecular weight surfactants. In this work, synthesis of amphiphilic double-brush copolymers (DBCs) and their application as bespoke macromolecular emulsifiers for the formation of IL-containing non-aqueous emulsions are described. DBCs consisted of a polyurethane (PU) backbone and poly(-dimethyl acrylamide) (PDMA) and poly(methyl methacrylate) (PMMA) chains that were grafted simultaneously at the same reactive site along the PU backbone (PU--PDMA/PMMA), which were synthesized through the combination of polyaddition and the reversible-deactivation radical polymerization reactions. Highly stable [Bmim][PF]-in-benzene emulsions could be gained by adopting PU--PDMA/PMMA DBCs as macromolecular emulsifiers at a low content, such as 0.025 wt %. On the basis of the stability and the size of emulsion droplets, PU--PDMA/PMMA DBCs exhibited much better emulsifying performances than their analogues, including PU--PDMA, PU--PMMA, and PDMA--PMMA copolymers. Such excellent emulsifying performances of PU--PDMA/PMMA DBCs were due to high interfacial activities. PU--PDMA/PMMA DBCs exhibited higher capabilities in lowering the interfacial tension of the [Bmim][PF]-benzene interface than their analogues. A large energy barrier to desorption of adsorbed PU--PDMA/PMMA DBCs from the interface contributed to high stability of the [Bmim][PF]-in-benzene emulsion.