Dynamic chitosan networks via Diels-Alder chemistry: Correlating molecular design, structure, thermo-responsive...

The development of bio-based polymeric materials from renewable resources is essential for reducing both environmental impact and dependence on fossil-derived materials. In this study, thermoreversible cross-linked networks were prepared by combining chitosan (CS) and a castor oil (CO) derivative through the Diels-Alder (DA) reaction. Furyl-functionalized CS was cross-linked with maleimide-modified CO to obtain bio-based polymer films. The influence of CS's degree of substitution (DS) and the furyl-to-maleimide (Fu:MI) ratio on the structural, thermal, mechanical, and antimicrobial properties was systematically investigated. The resulting networks demonstrated improved thermal stability compared to native CS, with the onset thermal decomposition raising from 46 °C (CS) to 79-131 °C (networks). Differential scanning calorimetry (DSC) confirmed the occurrence of the reversible retro-Diels-Alder (rDA) reaction between 103 and 115 °C. For the first time, the reproducibility of the rDA process in CS-based systems was demonstrated by successive DSC cycles, confirming their potential for recyclable and self-healing materials. Furthermore, the networks showed pronounced antimicrobial activity (up to 100 %), which increased with higher DS values, highlighting their applicability in areas such as biomedical coatings or packaging. This work provides a sustainable pathway for designing recyclable, antimicrobial materials by combining functionalized polysaccharides with renewable vegetable oils.