Chitosan modification with octenyl succinic anhydride (OSA): Effect of the degree of substitution on the structural, mechanical and barrier properties in the synthetized bioplastics

Chitosan is considered a promising biopolymer for replacing petroleum-based plastics due to its abundance, low production cost, biodegradability, and biocompatibility. However, its poor mechanical and barrier properties, along with high water solubility, limit its applications. This study analyses the effect of different degrees of modification on the physicochemical and film-forming properties of chitosan, as well as on the mechanical, physical and barrier properties of the developed films. FTIR and NMR analyses confirmed the successful incorporation of OSA groups into the biopolymer backbone, with crystalline structural changes observed by XRD at high degrees of substitution (DS). However, these structural modifications were not visible in SEM micrographs, where both control and modified chitosan films exhibited a similar compact and smooth matrix. Octenylsuccination of chitosan slightly improved the water vapour- and light-barrier properties of the films, as well as the mechanical properties of less modified films. Additionally, the incorporation of hydrophobic chains into the hydrophilic chitosan network significantly reduced film solubility from 58.86 % to 6.46 %. These results showed that the degree of modification of the chitosan plays a crucial role in the final properties of the films, which could potentially increase their range of applications. • Chitosan was successfully modified with increasing concentrations of OSA. •The chemical modification altered the crystalline structure of the biopolymer. •The incorporation of OSA molecules modified the film-forming behaviour of chitosan. •OSA-modified chitosan films exhibited a significant decrease in water solubility. •The OSA modification enhance the water barrier properties of the films.