Anti-oxidative and UV-absorbing biohybrid film of cellulose nanofibrils and tannin extract

Cellulose and tannin are both abundant and biodegradable natural polymers. This study proposes a strategy to construct biohybrid films combining the characteristics of cationic cellulose nanofibrils (CCNFs) and tannin extract for film applications. Multi-functional biohybrid films with anti-oxidative and UV-adsorbing characteristics were successfully fabricated from CCNF and tannin mixtures with different mass ratios. The results indicated that pure CCNF could be endowed with multi-functionality by a small amount of introduced flavonoid-rich tannin extract. By adding 5% (w/w) of extract, CCNF-tannin film achieved good anti-oxidant and UV-shielding ability, and simultaneously obtained ca. 15% improved thermal stability and tensile strength of up to 160 ± 9 MPa. In addition, tannin extract was able to enhance the optical clarity of CCNF film with tailorable appearances. The biohybrid films essentially consisted of renewable materials, and they can potentially be exploited in sustainable applications such as biocomposites and packaging materials.