Cationic Organosilicon Terpolymer-Modified Fibers via Synergistic Anchoring and Cross-Linking: A Fluorine-Free Strategy for High-Barrier Sustainable Packaging

Replacing plastic with paper is an important strategy for the green transformation of the packaging industry. However, paper exhibits limited barrier performance against liquids, oils, and gases because of the hydrophilicity of cellulose fibers and the porous structure of paper. To overcome these limitations, a novel fluorine-free cationic organosilicon terpolymer was developed by radical polymerization of [2-(acryloyloxy)ethyl]trimethylammonium chloride (DAC), 3-(tris(trimethylsiloxy)silyl)propyl methacrylate (TRIS), and allyl methacrylate (AMA) to create a protective barrier on fibers during paper formation. The terpolymer acted as a molecular barrier layer that reduced surface energy, enhanced fiber interfacial interactions, and improved the barrier properties of paper. The optimized terpolymer with a DAC/TRIS molar ratio of 1:1.4 significantly improved the performance of paper made from the modified fibers, reducing the Cobb60 value by 83% to 22.28 g/m 2, increasing the water contact angle to 124°, and achieving a Kit rating of 10 for oil resistance. In addition, the barriers against water vapor and oxygen were also notably improved. Molecular dynamics simulations showed that the optimized terpolymer exhibited a minimum surface energy of 0.1410 J/m 2, a maximum interfacial interaction energy of −316.35 kcal/mol, and the highest fractional free volume (0.1111), which together favored interfacial anchoring and hydrophobic barrier formation. Furthermore, Soxhlet extraction combined with inductively coupled plasma–optical emission spectrometry analysis revealed the coexistence of extractable and Soxhlet-resistant terpolymer fractions in the treated paper, indicating that the terpolymer was not merely deposited on the fiber surface but partially anchored within the fiber structure through stable interfacial interactions and physical entrapment. This strategy, combining cationic electrostatic anchoring and hydrophobic segment rearrangement, provides a promising route for developing high-performance, repulpable, fluorine-free paper-based packaging materials.