Influence of electronic effects from bridging groups on synthetic reaction and thermally activated polymerization of bisphenol-based benzoxazines

摘要

Six bis-benzoxazines based on bisphenols with different bridging groups, -C(CH_3)_2-, -CH_2-, -O-, -CO-, -SO_2-, and single bond, were synthesized in toluene. The influence of electronic effects from bridging groups on ring-forming reaction and thermal ring-opening polymerization were relatively discussed in detail. Their structures were characterized by high-performance liquid chromatography, Fourier transform infrared, 1H NMR, differential scanning calorimetry, and elementary analysis. The quantum chemistry parameters of the bisphenols and bis-benzoxazines were calculated by molecular simulation. The results indicated that the electron-withdrawing groups inhibited the synthetic reaction by decreasing the charge density of α-Cs of bisphenols and increasing energy barriers of the synthetic reactions. However, the electron-withdrawing groups promoted the thermally activated polymerization, which resulted from their activation energy and curing temperature decrease by increasing the bond length and lowering the bond energy of C-O on oxazine rings. Besides, because of stronger electron-withdrawing sulfone group, there were more arylamine methylene Mannich bridge structure in the polybenzoxazine.