Heteronucleobase-functionalized benzoxazine: synthesis, thermal properties, and self-assembled structure formed through multiple hydrogen bonding interactions

In this study we prepared a new class of thymine (T)-functionalized polybenzoxazine (PBZ) through the Michael addition of T to a new acryloyl-functionalized [(3-phenyl-3,4-dihydro-2H-benzooxazin-6-yl)methyl acrylate]benzoxazine (PA-ac) monomer and subsequent polymerization. We used 1H and 13C nuclear magnetic resonance spectroscopy and Fourier transform infrared (FTIR) spectroscopy to confirm the chemical structure of this new monomer and then employed differential scanning calorimetry (DSC) and FTIR spectroscopy to study the curing behavior of the new PBZ. The presence of the strongly self-complementary, multiply hydrogen-bonded T units in the PBZ matrix significantly enhanced its thermal stability, as evidenced from DSC traces and thermogravimetric analyses. Transition electron microscopy and wide-angle X-ray diffraction data provided evidence for the self-assembly of the PBZ occurring through self-complementary multiple hydrogen bonding of its T units.