Two formation mechanisms and renewable antioxidant properties of suspensible chitosan-PPy and chitosan-PPy-BTDA composites

► Suspensible chitosan-polypyrrole (CPC) composites by applying NaNO2 as oxidant. ► Porphyrin moieties in CPC composites. ► BTDA as cross-linking agent for suspensible chitosan-PPy-BTDA composites. (CPBC) ► Renewable antioxidant properties of CPBC films.