Janus-Like Single-Chain Polymer Nanoparticles as Two-in-One Emulsifiers for Aqueous and Nonaqueous Pickering Emulsions

The exploration of Pickering emulsions is very significant owing to their versatile and important applications in many scopes. In this study, synthesis of a novel kind of single-chain polymer nanoparticle (SCPN) and its stabilized Pickering emulsions were demonstrated. To this end, linear-dendritic diblock copolymers consisting of poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) blocks and four-generation dendritic aliphatic polyester blocks (G4) have been first synthesized by the combination of click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization reaction. The subsequent intramolecular cross-linking of the PDMAEMA block of PDMAEMA-b-G4 copolymers in DMF using 1,4-diiodobutane as cross-linkers afforded Janus-like SCPNs that exhibited a cross-linked PDMAEMA head tethered by a short dendritic tail. The molecular weight and distribution together with the structure of polymers were carefully characterized by GPC and NMR spectroscopy. By the employment of the as-synthesized Janus-like SCPNs as Pickering emulsifiers, aqueous and nonaqueous Pickering emulsions including water-in-oil and oil-in-oil as well as ionic liquid-in-oil were generated. Under the same conditions, it was found that the long-term stabilities of Pickering emulsions stabilized by Janus-like SCPNs were superior to those of Pickering emulsions stabilized by their linear quaternized PDMAEMA-b-G4 by CH3I analogous.