Structure-Function Relationships in Galactomannan Starch Films for Fast-Dissolving Applications: Effects on Physicochemical and Mechanical Properties.

Orally disintegrating films (ODFs) have attracted increasing attention because of their rapid disintegration and ease of administration. In this study, galactomannan-starch biopolymer films were developed as fast-dissolving oral film matrices using galactomannan extracted from Caesalpinia pulcherrima combined with corn and arrowroot (Maranta arundinacea) starches at different proportions. The effect of polymer composition on structure-function relationships was systematically investigated, with emphasis on how intermolecular interactions influence the physicochemical and mechanical properties of the films. Starch incorporation significantly affected polymer-network organization, leading to changes in rheological behavior, morphology, and macroscopic performance. Mechanical properties were strongly dependent on starch type: corn starch promoted greater flexibility, whereas arrowroot starch increased rigidity, likely because of differences in amylose content. The films exhibited homogeneous morphology, high transparency, and surface pH values close to neutrality. Water affinity and disintegration behavior were directly influenced by polymer composition, highlighting the role of polymer-polymer interactions in controlling hydration and the structural stability of the developed film matrices. Spectroscopic analysis suggested the presence of intermolecular interactions, particularly hydrogen bonding, which contributed to the modulation of film properties. Among the evaluated formulations, the system containing 75% galactomannan and 25% corn starch exhibited a balanced combination of mechanical strength, flexibility, and rapid disintegration. These findings demonstrate that galactomannan-starch blends are promising materials for ODF applications and provide insights into tailoring structure-function relationships in sustainable biopolymer systems.