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A bifunctional benzoxazine monomer, 6,60 -bis (3-methyl-3,4-dihydro-2H-benzo[e] [1,3]oxazinyl) sulfone (BS-m), was synthesized from bisphenol-S, methylamine, and formaldehyde via a solution method. The chemical structure of BS-m was characterized with 1 H and 13 C-nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The ring-opening polymerization reaction of BSm monomer was studied by FTIR, 13 C solid-state NMR, and differential scanning calorimetry. With the polymerization reaction proceeding, the intensities of the FTIR absorption peaks of CH 2 , CAOAC, and CANAC of the oxazine ring decreased gradually, and some of these absorption peaks disappeared. The shapes and intensities of the absorption peaks associated with benzene ring, sulfone group, and aromatic CAS bond changed in various ways. The changes in the solid-state 13 C-NMR pattern, including chemical shifts, intensity of resonances, and line-width, were observed from the spectra of BS-m and the corresponding polybenzoxazine. The melting process of BS-m overlapped with the beginning of the ring-opening polymerization reaction. The polymerization kinetic parameters were evaluated for nonisothermal and isothermal polymerization of BS-m.

Poly(benzoxazine-co-urethane) was prepared by meltblending bisphenol-S/aniline-type benzoxazine (BS-a) with isocyanate-terminated polyurethane (PU) prepolymer based on 2,4-toluene diisocyanate and poly(ethylene glycol), followed by thermally activated polymerization of the blend. The copolymerization reaction between BS-a and PU prepolymer was monitored using Fourier transform infrared spectroscopy. The morphology, dynamic mechanical properties, and thermal stability of the poly(benzoxazine-co-urethane) were studied using scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry. Homogeneous morphology is shown in scanning electron micrographs of the fracture surfaces of poly(benzoxazine-co-urethane)s with different urethane weight fractions, and the roughness of the surface increases with urethane content increasing. Correspondingly, a single glass transition temperature (T g ) is shown on the dynamic mechanical analysis curves of the poly(benzoxazine-co-urethane)s, and the T g is higher than that of the polybenzoxazine. With increase in the urethane content, the T g and water absorption of poly(benzoxazine-co-urethane) increase, whereas the storage modulus and thermal stability decrease.

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