Development of nanocurcumin-embedded poly(styrene-co-allyl alcohol) nanocomposites with enhanced functional properties for sustainable food packaging

Poly (styrene- co -allyl alcohol) (PSSA)/nanocurcumin (Cur) composites were successfully prepared through a facile solvent-free mechanical grinding technique to develop multifunctional materials for advanced functional and active food-packaging applications. The physicochemical, optical, thermal, morphological, electrical, mechanical, antioxidant, and food preservation properties of the prepared nanocomposites (NCs) were systematically characterized by FTIR, XRD, UV–Vis spectroscopy, FE-SEM, DSC, TGA, impedance analysis, tensile testing and DPPH radical scavenging assay. FTIR analysis demonstrated successful chemical bonding between the copolymer and Cur, as evidenced by the new absorption band at 450 cm −1 . The copolymer NCs displayed improved UV absorption, indicating enhanced UV-shielding capabilities, coupled with a gradual reduction in optical bandgap, implying enhanced charge-carrier mobility. XRD measurements demonstrated an improvement in crystallinity with increasing Cur concentration. FE-SEM images reveal a distinct morphological shift in the copolymer-decorated NCs at varied ratios. Thermal studies exhibited higher glass transition temperatures and thermal stability with increasing Cur concentrations. Electrical characterization indicated decreased activation energy and temperature-dependent increase of dielectric constant and AC conductivity, suggesting increased charge transfer. The PSSA containing 5 wt% nanocurcumin displayed increased mechanical properties with tensile strength and Young’s modulus increasing from 30.63 to 44.91 MPa and 1.42 to 2.33 GPa, respectively. The copolymer NCs also displayed improved antioxidant activity, with the DPPH radical scavenging efficiency increasing significantly upon the addition of nanocurcumin and reaching its maximum at 5 wt% loading, demonstrating the effective free radical scavenging capability of nanofiller. Moreover, tomatoes packaged using PSSA/Cur-coated paper remained fresh for up to 40 days. Overall, nanocurcumin reinforcement imparted multifunctional properties to the PSSA matrix by simultaneously enhancing its structural, optical, thermal, electrical, mechanical, antioxidant and food-packaging performance, making the developed NCs promising candidates for advanced functional and active food-packaging applications.