Effect of surface chemistry on the dispersion and pH-responsiveness of chitin nanofibers/natural rubber latex nanocomposites

Chitin nanofibers (ChNFs) have emerged as a rising nanomaterial due to their excellent mechanical properties, biocompatibility and biodegradability etc. Herein, carbonylated ChNFs (C-ChNFs) and zwitterionic ChNFs (NCChNFs) decorated with both amino (-NH2) and carboxyl (-COOH) groups were used to prepare ChNFs/natural rubber (NR) nanocomposite films by dip molding method, respectively. The results showed that C-ChNFs had better dispersion than that of NC-ChNFs in NRL matrix. Moreover, C-ChNFs/NR nanocomposite films demonstrated obvious pH-responsiveness owing to the association and disassociation of the hydrogen bonding between C-ChNFs under various pH conditions. In contrast, NC-ChNFs/NR nanocomposite films showed pH-stable mechanical properties because the protonation of -NH2 at pH < 7 and the ionization of -COOH at pH > 7 resulted in electrostatic repulsive force between NC-ChNFs. This study demonstrates that surface chemistry of ChNFs plays an important role on tailoring the performance of ChNFs/NRL nanocomposites.