Effect of Molecular Structure on Polymerization and Dynamic Exchange Reactions in Benzoxazine/Polyetheramine-Based Covalent Adaptable Networks

Benzoxazine/polyetheramine-based vitrimers are synthesized through the polymerization of bisbenzoxazine in the presence of polyetherdiamine, resulting in aminoalkylated phenols that are capable of engaging in nucleophilic substitution-like covalent amine exchange reactions. To examine the effect of benzoxazine’s molecular structure on these reactions, seven model monobenzoxazines with varying electronic properties and substituent configurations were synthesized and reacted with a polyether monoamine. This study found that the molecular architecture of benzoxazine significantly impacts the rate and outcome of the ring-opening reaction and the benzoxazine/amine reaction. Notably, N-phenyl benzoxazines facilitate the formation of vitrimer-analogous polyether-aminoalkylated phenols, essential for the amine exchange reaction, whereas N-cyclohexyl benzoxazines do not undergo this reaction and are unsuitable for vitrimer formation. Additionally, electron-deficient benzoxazines demonstrate higher reaction rates in both the benzoxazine/amine and amine exchange reactions. This research highlights the crucial role of the benzoxazine structure in determining the efficiency and feasibility of the formation of dynamic vitrimer systems.