Density functional theory calculations on the grafting copolymerization of 2-substituted aniline onto chitosan

Chitosan is a biodegradable natural polymer which is safe and non-toxic and used in different applications. Grafting of chitosan with aniline derivatives is an important route to improve its properties. Chitosan has different active groups that can be blocked in the grafting process, which could be confirmed by calculation studies. The author thinks that the confirmation of chitosan active group included in the grafting by calculations is not given before. So authors give evidence to the direction of grafting and mechanism. Poly(2-methylaniline) (P2-MA), poly(2-hydroxyaniline) (P2-HA) and their copolymers are used in the present study. Quantum mechanics calculations using density functional theory were applied to study the grafting process. The obtained data reveal that grafting occurs at NH₂ groups, which is less energetic (2.04). This conclusion confirms the experimental studies. Computational calculations show that the interaction between chitosan and both P2-MA and P2-HA takes place at the NH₂ group of chitosan with high stabilization energy (− 1346.7746). A complete next-to-leading order (NLO) values show that the graft could be a better candidate for NLO application (42.25 kcal mol⁻¹) global properties (hardness). Also, the grafting process gives high reactive products due to a decrease in band gap energy.