Simultaneous improvement of mechanical strength and ductility of Sulfanilic acid-functionalized colloidal kraft lignin/methylcellulose biocomposite with excellent UV-shielding and antioxidant properties

The potential of colloidal kraft lignin (CKL) to replace petroleum-derived polymer composites while enhancing their functionalities has unlocked exciting opportunities for advanced applications. However, to leverage the beneficial properties of CKL in biocomposites requires the development of an efficient process for the synthesis of CKL particles with high yields. In this study, we develop a novel method for the eco-friendly production of CKL with high yield from a highly concentrated aqueous paste of functionalized KL with diazonium salt of sulfanilic acid (SA). The concentrated KL-g-SA paste with 50 wt% solid content was obtained via surface functionalization of KL through diazo coupling reaction between KL and diazonium salt of SA, followed by repeated washing and centrifugation, and collecting them without drying. Finally, the potential of synthesized KL-g-SA colloidal particles for the fabrication of an environmentally friendly biocomposite of methylcellulose with simultaneously enhanced mechanical strength and ductility, excellent antioxidant, and UV-blocking capabilities, along with additional functionalities, has been explored. • Novel strategy for functionalization (KL-g-SA) and processing of kraft lignin • Interfacial interactions of KL-g-SA with methylcellulose (MC) • Simultaneous improvement of mechanical strength and ductility • Substantially improved UV-shielding, and antioxidant functionalities