On the mechanism for the highly sensitive response of cellulose nanofiber hydrogels to the presence of ionic solutes

Abstract Hydrogels formed by cellulose nanofibers (CNFs) find use in a variety of applications. CNF hydrogels generally stiffen and ultimately flocculate with increasing salt concentrations. While charge repulsion explains the behavior nanocellulose variants that have been stabilized charged groups, it has puzzle why ions such pronounced effect also on CNFs unmodified surfaces. We studied ionic solutes native hydrogels, found already at very low concentrations around 1 mM, cause crowding hydrogels. The used were NaCl, Na 2 SO 4 , NaI, NaSCN, sodium acetate. For we densities which lead to relatively weak gels highly sensitive salts. Screening electrical double layer could not explain results ion To understand cellulose-ion interactions, computational molecular dynamics simulations. provide an explanation structure hydration layers cellulose. Understanding how affect properties can help for example manufacture when using as material components, substrates enzymes, or rheology modifiers. Ion-effects may be important more fundamental understanding interfacial interactions water under different conditions. Graphical abstract