Aqueous amidation of carboxymethylcellulose using dmtmm: toward functional paper coatings

This work reports the first successful application of octylamine-grafted carboxymethylcellulose (CMC-g-Oct)) as a sustainable coating for producing highly hydrophobic and oil-resistant paper. The grafting of CMC was carried out in water using 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM) as a condensing agent, at different DMTMM/carboxylate ratios (0.5–2 mol/mol). The degree of substitution of amidation (DSA) was quantified by 1H NMR and elemental analysis, yielding CMC-g-Oct materials with DSA values of 0.07, 0.14, and 0.24. Films prepared from these materials were characterized via ATR-FTIR, TGA/DSC, UV-Vis, moisture uptake (MU%), and water vapor permeability (WVP). The most performing film (DSA = 0.24) showed a 64% decrease in MU% and 60% reduction in WVP compared to unfunctionalized CMC film. This formulation was selected for paper coating, applied in up to three layers. The coated papers exhibited enhanced barrier performance, with contact angles up to 105 ± 8°, and significant reductions in WVP (56%) and oil permeability (99.8%). These findings highlight the strong potential of bio-based CMC-g-Oct coatings in replacing conventional fossil-derived packaging materials.