Effect of N-substituents on the surface characteristics and hydrogen bonding network of polybenzoxazines

In our study, the effect of N-substituents on the surface free energy and hydrogen bonding network structure of polybenzoxazine has been studied systematically. The contact angle measurement results show the surface energies of the polybenzoxazines decrease with the increase of alkyl chain length, and are not affected by the steric factor of the tert-butyl group. However, the FTIR curve fitting results show that both the chain length and bulkiness of alkyl group have an effect on the hydrogen bonding network of the polybenzoxazines, and facilitate the formation of intermolecular hydrogen bonding during the progress of cure. This indicates that both alkyl group and the fraction of intermolecular hydrogen bonding have an effect on the surface energy of the polybenzoxazines. Additionally, the transformation mechanism of the intermolecular and intramolecular hydrogen bonding during the progress of cure is proposed for the first time.