Structural alterations in nano-reinforced corn starch-based films: Fourier Transform Infrared Spectroscopy (FTIR) analysis

Abstract

Bioplastics derived from renewable resources like corn starch are gaining attention as sustainable alternatives to conventional plastics. Due to the poor polymer matrix and lack of mechanical properties, their wide range of usage is limited. Their properties can be significantly enhanced by the incorporation of nanomaterials. This study investigates the structural modifications induced by various nanomaterial reinforcements in corn starch-based bioplastics using Fourier Transform Infrared Spectroscopy (FTIR). Bioplastic films were synthesised by incorporating chitosan, carbon spheres, carbon quantum dots (CQDs), reduced graphene oxide (rGO), and titanium dioxide (TiO2) nanoparticles into a starch-glycerol matrix. FTIR analysis revealed key absorption bands corresponding to the characteristic functional groups of starch, glycerol, and the incorporated nanomaterials. These indicate chemical interactions and modifications within the polymer matrix. All films exhibited a broad O-H stretching band near 3322 cm-1 and C-H stretching vibrations at approximately 2931 cm-1. The hydration water in amorphous starch regions was confirmed by the H-O-H bending peak at 1654 cm-1. The glycosidic backbone’s C-O-H stretching vibrations appeared around 1150 cm-1. Notably, the -CH2 scissoring band shifted from 1455 cm-1 in pristine films to 1418 cm-1 upon nanomaterial incorporation. That signifies enhanced hydrogen bonding and improved interfacial interactions between starch and nanomaterials. The disappearance of the 1340 cm-1 O-H bending peak in CQDs and chitosan-reinforced films suggested strong hydrogen bonding engagement with nanomaterials. A consistent sharp peak at 996 cm-1, associated with glycosidic C–O–C vibrations, confirmed the retention of starch’s polysaccharide backbone after nanomaterial incorporation. The unique appearance of a 1027 cm-1 peak in TiO2-reinforced films was attributed to Ti–O–C bridging vibrations. This indicates the formation of a chemical linkage between TiO2 and starch. These spectral changes collectively demonstrate that nanomaterial incorporation induces significant structural alterations and enhances filler–matrix compatibility. Furthermore, these findings confirm the efficacy of nanomaterial reinforcement in tailoring the structure of starch-based bioplastics for improved performance.