Divanillin Cross-Linked Recyclable Cellulose Networks.

A series of cellulose networks are designed by reversibly crosslinking amino-functionalized 2-hydroxyethyl cellulose (HEC-NH₂) with different amounts of vanillin dimer (VA-CHO). The Schiff base reaction between amino-and aldehyde groups creates networks (SBHEC) bridged with crosslinks containing dynamic imine groups. These SBHEC networks can be hot pressed to flexible films with good thermal stability and solvent resistance, including notable stability in water, opposite to water-soluble HEC and HEC-NH₂. Compared to HEC-NH₂, the cross-linked SBHEC networks exhibit higher glass transition temperatures, elastic modulus, and tensile stress at break, and slightly reduced tensile strain at break. Reprocessing of the SBHEC networks is achieved through hot pressing under facile conditions, leading to good recovery of mechanical properties. Furthermore, the materials can be chemically recycled in a closed-loop by imine-hydrolysis under acidic conditions at room temperature. This releases the original building blocks HEC-NH₂ and VA-CHO, which can be recured to produce new SBHEC. This work highlights the potential of dynamic covalent cellulose networks as mechanically and chemically recyclable materials, contributing to the development of closed-loop recycling systems.