The first observation on polymerization of 1,3-benzothiazines: synthesis of mono- and bis-thiazine monomers and thermal properties of their polymers

A monofunctional 1,3-benzothiazine (PH-a-BZT) has been synthesized by a method different from the one reported in the literature. Additionally, a difunctional version of 1,3-benzothiazine (PH-ddm-BZT) monomer has been synthesized. Polymerization of mono- and bis-thiazine monomers has been studied and confirmed for the first time. The two monomers are characterized with proton and carbon nuclear magnetic resonance spectroscopy (1H-NMR, 13C-NMR) along with Fourier transform infrared (FT-IR) spectroscopy. The cross-linked polybenzothiazine which is derived from the bis-thiazine monomer shows excellent thermal properties as examined by thermogravimetric analysis (TGA). Polybenzothiazine is developed in hopes that it could mimic many of benzoxazine's popular attributes while containing sulfur in place of oxygen atoms. It can also possess unique advantages such as higher flame retardancy and adhesiveness to the metal substrate than polybenzoxazine due to the characteristic sulfur atom in its polymer.