Hydrophobization of carboxymethyl cellulose by Passerini reaction: towards films with improved water vapor barrier properties

To address the need for developing sustainable materials with effective barriers to water vapor, this work explores the potential of self-supported films made of carboxymethyl cellulose (CMC) functionalized by the Passerini three-component reaction. Aliphatic aldehydes and tert -butyl isocyanide were grafted onto CMC backbone to yield dually hydrophobized derivatives. These modified polysaccharides were processed into films by solvent casting and their water vapor transfer properties were examined. Small-angle X-ray scattering (SAXS) experiments revealed a nanoscale organization for Passerini-modified films, attributed to the formation of hydrophobic domains characterized by a nanometric interdomain spacing. Dynamic vapor sorption (DVS) analysis demonstrated a significant reduction in moisture content water for modified films, from ≃ 1.1 g.g −1 for unmodified CMC to below 0.5 g.g -1 for hydrophobized derivatives at a w = 0.95. Guggenheim-Anderson-deBoer (GAB) and Zimm-Lundberg modeling showed a decrease in sorption site availability from 3 to ≃ 1.5 per glucose unit, while the size of water clusters was significantly increased. The Passerini modification also resulted in a substantial decrease of water vapor permeability (WVP) from 44 000 barrer to 2 500 barrer at a w = 0.5. These results unequivocally underpin the benefits of the Passerini functionalization which allows to enhance the water vapor barrier performance. The findings highlight the potential of such a reaction for developing next-generation and bio-based packaging materials with tailored water vapor barrier properties. • The Passerini reaction allows the formation of dually hydrophobized self-standing CMC-based films • SAXS evidences a nanoscale structuration resulting from hydrophobic aggregated domains • Equilibrium water sorption is reduced from 1 to 0.5 g.g −1 at a w = 0.95 • Water vapor permeability decreased from 44 200 to 2 500 barrer at 25 °C and a w = 0.5 .