Encapsulation of hygroscopic liquids via polymer precipitation in non-aqueous emulsions

Hypothesis: Encapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limita-tions associated with bulk materials, e.g., slow mass transfer rates, high viscosities, or susceptibility to external environment. Single step soft-templated encapsulation methods commonly use interfacial poly-merization for shell formation, with a multifunctional monomer in the continuous phase and another in the discontinuous phase, and thus do not give pristine core material. We posit that polymer precipitation onto emulsion droplets in non-aqueous emulsions could produce a robust shell without contamination of the core, ideal for the encapsulation of water-sensitive or water-miscible materials. Experiments: Solutions of commodity polymers were added to the continuous phase of non-aqueous Pickering emulsions stabilized by alkylated graphene oxide (GO) nanosheets such that the change in sol-ubility of the polymer led to formation of robust shells and the production of capsules that could be iso-lated. Findings: We demonstrate that a polymer precipitation approach can produce capsules with pristine core of the IL 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF6] or the salt hydrate PCM mag-nesium nitrate hexahydrate (MNH) and shell of nanosheets and polystyrene, poly(methyl methacrylate), or polyethylene. The capsules are approximately 80 wt% [Emim][PF6] or > 90 wt% MNH, and the core can undergo multiple cycles of solidification and melting without leakage or destruction. This novel, single-step methodology provides a distinct advantage to access capsules with pristine core composition and is amenable to different core and shell, paving the way for tailoring capsule composition for desired applications. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

Encapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limitations of bulk materials. The use of a polymer precipitation approach in non-aqueous emulsions can produce capsules with a pristine core and a robust shell, suitable for water-sensitive or water-miscible materials.