Oxidation-Responsive Emulsions Stabilized by Cleavable Metallo-Supramolecular Cross-Linked Microgels

Abstract

An original route to develop an advanced class of microgels emulsifiers containing stimulable metallo-supramolecular instead of frozen covalent crosslinks is reported. The poly(Nisopropylmethacrylamide) (PNiPMAM) chains of the microgel are connected by iron(II)bis(terpyridine) coordination supramolecular complexes that can be cleaved on demand leading to unique properties both at interfaces and in volume. The microgels synthesis is undemanding and the characterization of their supramolecular structure can be precisely achieved by standard methods.Singularly, interfaces of an oil-in-water emulsion stabilized by the supramolecular particles can be triggered at molecular scale by oxidation of Fe(II) to Fe(III), leading to emulsion breaking. In bulk, we show that a microgel dispersion can indeed be transformed into a polymer solution upon oxidation. Our study paves the road to the discovery of unusual microgel properties as our proof-of-concept can be extended to different supramolecular chemistry and architecture.

Magneto-Responsive Nanocomposites with a Metal–Ligand Supramolecular Matrix

“…Since the attribution of the Nobel Prize in Chemistry to Cram, Lehn, and Pedersen for their pioneering research on supramolecular chemistry, the interest of the scientific community for supramolecular materials has continuously grown. In particular, supramolecular polymers and networks based on various interactions such as hydrogen bonds, π–π interactions, ionic aggregation, and metal–ligand complexation have since seen incredible development, notably as bases for self-healing-oriented applications. − Among these supramolecular interactions, metal–ligand interactions are particularly interesting because their characteristics (binding strength, lifetime) can be tuned over several orders of magnitude simply by changing the metal ions and/or the ligand. , Among a myriad of available ligands, terpyridine (TPy) has been widely used to form a variety of supramolecular polymers and networks because of its relatively easy synthesis, existence of several commercially available derivatives, and ability to coordinate with a broad range of transition metal ions. − …”

Engineering hybrid microgels as particulate emulsifiers for reversible Pickering emulsions

“…18 Since then, numerous studies have been reported on microgel-stabilized emulsions 19 with a variety of responses, including CO2/N2, sugar addition, 20 magnetic field, 21 and oxidation. 22 Typically, microgels are highly hydrophilic and preferentially stabilize o/w Pickering emulsions. 23,24 However, only forming o/w emulsions has application limitations, particularly in the preparation of aqueous-core microcapsules, 25 interfacial biocatalysis, [26][27][28][29] gene delivery, 30 and encapsulation of watersoluble actives.…”

“… 18 Since then, numerous studies have been reported on microgel-stabilized emulsions 19 with a variety of responses, including CO 2 /N 2 , sugar addition, 20 magnetic field, 21 and oxidation. 22 …”

Responsive Polyphenol‐Crosslinked Supramacromolecular Microgels with pH‐Triggered Disassembly in Aqueous Solution

“…[49] Recently, Es Sayed et al demonstrated the synthesis of supramacromolecular microgels by first preparing non-crosslinked microgels by copolymerization of N-isopropyl methacrylamide together with a terpyridine-based semi-crosslinker, which were then supramolecularly crosslinked in a second step by the addition of iron (II) through metal complexation. [50] Another possibility is the incorporation of host-guest interactions using methacrylated 𝛽-cyclodextrine with polyanions, [51] cholesterol, [52] or vinylferrocene [53] as guest molecules. Another phenolic crosslinker used to synthesize physically crosslinked PVCLbased microgels using free radical precipitation polymerization is (+)-catechin hydrate.…”