Controlled Sol–Gel Transitions of Metal–Organic Membrane-Enveloped Cellulose Nanofibrils via Metal Coordination in Aqueous Media

Abstract

We report a metal coordination-driven sol−gel transition system where cellulose nanofibrils are enveloped by a rationally designed metal−organic membrane (MOM) in an aqueous medium. Specifically, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) is encapsulated within an MOM comprising Zn 2+ and the chelator phytic acid (PA), denoted TOBC MOM . Using the DLVO theory, we elucidate how tuning the metal ion valence in TOBC MOM modulates the sol−gel transition by controlling interfibrillar attractive forces. Notably, TOBC MOM fluids exhibit relaxation times consistent with the Kohlrausch−Williams−Watts (KWW) function. Significantly, we demonstrate reversible, sustainable sol−gel transitions in TOBC MOM under stepwise mechanical strain. This facile approach enables rheological tailoring of aqueous media, promising for the development of advanced stimuli-responsive smart fluids for applications in cosmetics, food science, and pharmaceutical formulations.