Engineering high-barrier biopolymer films derived from Sargassum via dual-alginate blending

The development of high-performance biopolymer films with tunable structure and property relationships remains a key challenge in sustainable materials science. Sargassum , an abundant brown macroalgal biomass inundating coastal zones, presents severe ecological, environmental, and economic challenges while offering a promising yet underutilized source of alginate for advanced material applications. However, films derived solely from Sargassum -based alginate exhibit intrinsically poor mechanical strength, thermal stability, and barrier properties, limiting their viability for high-performance applications. In this study, a dual-alginate blending strategy is introduced to engineer high-barrier biopolymer films by combining Sargassum -derived alginate with commercial variants (Sigma, Protanal, and Manugel). This approach enables systematic modulation of polymer composition by tuning the mannuronic-to-guluronic (M:G) ratio and molecular weight to enhance performance. Among the systems evaluated, Sargassum –Manugel blends exhibited superior properties, with performance trends supported by multi-criteria decision analysis. Results indicated that the 1:2 Sargassum -Manugel blend delivered the most improvements, with tensile strength (σ) increasing from 2.89 to 10.55 MPa, water vapor permeation (WVP) decreasing from 8.89 × 10⁻¹ ² to 2.15 × 10⁻¹ ² g m/m² s Pa, and oxygen permeability (OP) dropping by over 96% (from 118.47 to 2.49 cm³ μm/m² d kPa) compared to pure Sargassum films—surpassing many petroleum and biopolymer alternatives. Thermogravimetric analysis (TGA) and FTIR spectroscopy revealed enhanced thermal stability and the formation of a more cohesive polymer network, indicating strong intermolecular interactions and elucidating composition–structure–property relationships. This work establishes a novel multicomponent alginate platform and a scalable design framework for engineering high-performance polysaccharide-based materials, providing a foundation for next-generation functional biomaterials across packaging and advanced materials applications.