Reversible Assembly of Microgels by Metallo‐Supramolecular Chemistry

Abstract

The combination of supramolecular chemistry and soft colloids as microgels represents an ambitious way to develop multi‐versatile colloidal assemblies. Hereafter, terpyridine‐functionalized poly(N‐isopropylacrylamide) (PNiPAM) microgel building blocks are shown to undergo an assemble–freeze–disassemble process. The microgel assemblies, which are controlled by monitoring the attractive and repulsive potentials between the soft colloidal particles, are then frozen by forming inter‐particle metal–terpyridine bis‐complexes upon addition of the metallic cation (such as FeII, CoII). By oxidation of the metal–terpyridine bis‐complex links, the aggregates open up, which is due to the complex dissociation releasing the connected particles in the form of single microgels. We extended our work to the development of 1D filaments and 2D membranes materials made of soft particles connected via supramolecular chemistry.

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

“…More precisely, hydrogen peroxide (H 2 O 2 ) and potassium persulfate (KPS) were used to oxidize into iron (III) the iron(II) embedded between the terpyridine units. 44,45 The pictures presented on Figure 2b clearly show that 12 hours after addition of either H 2 O 2 or KPS to the microgel dispersion, the pink color has totally vanished to give a non-turbid colorless solution. The disappearance of the [Fe II Tpy 2 ] 2+ complex is also evidenced for both oxidizer molecules by the loss of the absorption band at 556 nm, characteristic of the Fe(II) complex, in the UV/Vis spectrum (Figure 2a).…”