Polymerization of linear aliphatic diamine-based benzoxazine resins under inert and oxidative environments

A series of linear aliphatic diamine-based benzoxazine monomers have been studied. Reaction times and purification procedures have been optimized for each individual diamine. The structure of these diamine-based benzoxazine monomers has been characterized by 1H and 13C NMR, and infrared spectroscopy. The rate of polymerization has been studied by Fourier transform infrared spectroscopy as a function of the chain length of the aliphatic amines. The glass transition temperatures (Tg) of the polybenzoxazines from these monomers are also studied. The short chain amine polybenzoxazine exhibits the Tg of around 170 °C. The influence of the polymerization environment for these linear aliphatic diamine-based series of benzoxazine monomers has been studied under air and inert atmosphere. Differential scanning calorimetry is used to determine the melting points of these benzoxazines and the temperature of the peak polymerization exotherm. An anomalous polymerization behavior of ethylene diamine-based polybenzoxazine is also reported.