Water-Driven Sol–Gel Transition in Native Cellulose/1-Ethyl-3-methylimidazolium Acetate Solutions

Abstract

The addition of water to native cellulose/1-ethyl-3methylimidazolium acetate solutions catalyzes the formation of gels, where polymer chain−chain intermolecular associations act as cross-links. However, the relationship between water content (W c ), polymer concentration (C p ), and gel strength is still missing. This study provides the fundamentals to design water-induced gels. First, the sol−gel transition occurs exclusively in entangled solutions, while in unentangled ones, intramolecular associations hamper interchain cross-linking, preventing the gel formation. In entangled systems, the addition of water has a dual impact: at low water concentrations, the gel modulus is water-independent and controlled by entanglements. As water increases, more cross-links per chain than entanglements emerge, causing the modulus of the gel to scale as. Immersing the solutions in water yields hydrogels with noncrystalline, aggregate-rich structures. Such water−ionic liquid exchange is examined via Raman, FTIR, and WAXS. Our findings provide avenues for designing biogels with desired rheological properties.