Tuning Structure and Rheological Properties of Polyelectrolyte-Based Hydrogels through Counterion-Specific Effects

• DOI: 10.1021/acs.macromol.2c01565
• Publication Date: 2023-01-20T15:31:31Z
• Authors: Claire Hotton; Guylaine Ducouret; Juliette Sirieix-...; Thomas Bizien; Lionel Porcar; Natalie Malikova
• Keywords: Divalent; Small-angle X-ray scattering

Tuning at will the properties of gel-forming systems is key relevance for many biotechnological, agricultural, and biomedical applications. For polyelectrolyte-based gels, ion-specific effects can be an attractive way this purpose. This study investigates counterion-specific effect on microscopic structure rheological a physical hydrogel formed ionene-type cationic polyelectrolytes. The focus two monovalent halide counterions (F– Cl–) divalent counterion (SO42–). A strong appears within ionene-based gels. In case counterions, gelation more effective weakly hydrated counterions. Indeed, strongly maintain electrostatic repulsions between chains as consequence gel formation shifted toward higher concentrations (higher critical concentration, CGC). combination complementary small-angle X-ray neutron scattering (SAXS SANS) techniques reveals contribution ion–ion correlations in network. Contrary to chloride which present single correlation length characterizing distance cross-linking nodes, fluoride gels additional network nodes. accompanied by very rapid increase elastic modulus once CGC reached. With even remarkable with lower equivalent polyelectrolyte concentrations. presence favors association chains, probably bridging effect. evokes "egg-box" model, characteristic scaling reduced concentration confirms this. However, only narrow window exists before precipitation takes over due too chain–chain interactions.