Superchaotropic Nano‐ion Binding as a Gelation Motif in Cellulose Ether Solutions. Issue 3 (13th December 2022)

• Record Type: Journal Article
• Authors: Hohenschutz, Max; Bauduin, Pierre; Lopez, Carlos G.; Förster, Beate; Richtering, Walter
• Is Part Of: Angewandte Chemie international edition. Volume 62:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-13
• Subjects: Cellulose -- Chaotropic Effect -- Hydrogel -- Polyoxometalate -- Superchaotropic; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202210208
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Nanometer‐sized anions (nano‐ions) like polyoxometalates and boron clusters exhibit so‐called superchaotropic behavior, which describes their strong binding to hydrated non‐ionic matter in water. We show here that nano‐ions, at millimolar concentrations, dramatically enhance the viscosity and induce gelation of aqueous solutions of non‐ionic cellulose ethers (CEs), a class of widely utilized polymers known for their thickening and gel‐forming ability. These phenomena arise from an interplay of attractive forces and repulsive electrostatic forces between CE‐chains upon nano‐ion binding. The attractive forces manifest themselves as aggregation of CE‐chains into a physically crosslinked polymer network (gel). In turn, the electrostatic repulsions hamper the viscosity increase and gelation. Superchaotropic nano‐ion binding emerges as a novel and general physical crosslinking motif for CE‐solutions and exceeds by far the conventional thickening effects of classical salts and ionic surfactants. Abstract : Nano‐ions, like polyoxometalates and boron clusters, co‐assemble strongly with non‐ionic solutes in water driven by the chaotropic effect. Here, nano‐ion assembly with non‐ionic cellulose ethers (CE) is shown to result in unprecedented thickening effects and gelation of CE‐solutions. An interplay of electrostatic repulsion and attraction between chains arises upon nano‐ion adsorption to the CE‐polymer and provides a facile novel way of gelling CEs.