Balancing Water Uptake, UV Visible Screening, and Mechanical Strength in Cellulose Alginate Quercetin Hydrogel Films

Combining high water affinity and strong UV-vis shielding while preserving mechanical performance in fully biobased cellulose films remains challenging, as hydrophilic polysaccharide modifiers and polyphenolic additives can disrupt network cohesion, promote phase-enriched domains, and trigger early fracture. Here, renewable hydrogel films were engineered from bleached Eucalyptus cellulose by incorporating sodium alginate (SA) and quercetin (Q) as multifunctional additives to tune structure-property relationships. Composite hydrogels were homogenized under a standardized and scalable protocol and converted into continuous films by doctor blade coating. Film morphology, intermolecular interactions, crystallinity, optical response, wetting and hydration, and tensile behavior were assessed by FE-SEM, ATR-FTIR, XRD, UV-vis spectroscopy, contact-angle kinetics, gravimetric water uptake, and tensile testing. Quercetin governed the visible color shift and enabled strong UV-vis attenuation (>95%), whereas alginate improved film continuity and enhanced hydration. FTIR and XRD supported predominantly noncovalent incorporation, consistent with a physically cross-linked polysaccharide network. An optimum formulation, CEL-2SA-1Q (97/2/1 wt %), delivered the highest mechanical performance (F _max = 147.85 ± 9.82 N, UTS = 67.20 ± 4.46 MPa, and Young's modulus = 1411.3 ± 18.3 MPa), corresponding to ∼1.5× higher F _max and UTS and 2.75× higher modulus than neat cellulose films. The same formulation showed enhanced hydrophilicity, with the contact angle decreasing to ∼35° within 60 s and a 24 h water uptake about 3-fold higher than neat cellulose. These combined attributes suggest the potential of the optimum film as a prospective fully biobased, high-absorbency, UV-vis-opaque liner for sustainable packaging of high-moisture, light-sensitive products, where exudate retention and photoprotection are critical for preserving appearance and delaying oxidation.