Benzoxazine monomers containing triphenylimidazole: Polymerization of monomers and properties of polybenzoxazines

In this study, two novel benzoxazine monomers containing triphenylimidazole (TBZ) and triphenylimidazolium (MTBZ) moieties are synthesized and fully characterized. The thermal ring-opening polymerization process of the two monomers is monitored by the 1H NMR and GPC analyses, which demonstrates that such a polymerization proceeds through a rearrangement of ketal-type linkage in the main chain into Mannich-type polymer along with the fast increasing in molecular weight. The structures of the triphenylimidazole-containing polybenzoxazines, poly-TBZ and poly-MTBZ, are verified by 1H NMR and FT-IR spectroscopies, and the thermal and mechanical properties of such polybenzoxazines are investigated by TGA and DMA analyses. Owing to the good solubility of poly-TBZ and poly-MTBZ in common organic solvents, poly-TBZ can be easily converted into poly-MTBZ through a facile post-modification approach. More importantly, the poly-TBZ shows the acid-dependent spectral properties due to formation of amine salts, whereas poly-MTBZ can be used as a chemodosimeter for the detection of Ag+, which exhibits high selectivity, good linearity and naked-eye distinguishable color change. This strategy can be utilized to prepare triphenylimidazole-containing polybenzoxazines with good solubility and tunable spectral properties, thereby extending their functionalities and applications.