Benzoxazines derived from bisphenol-A, formaldehyde, and primary amines were characterized using 13C solid-state NMR spectroscopy. The two 1,3-benzoxazines studied in this work are 2,2′-(3-methyl-4-dihydro-1,3,2-benzoxazine)propane, (B-m) and 2,2′-(3-phenyl-4-dihydro-1,3,2-benzoxazine)propane (B-a). Solid-state 13C-NMR spectra were obtained for B-m and B-a and the observed peak positions were noted. These resonances agreed well with chemical shifts calculated based on the chemical structure. Samples of B-m and B-a were cured at two different temperatures: 150 and 200°C. The polymerizations induced spectral changes including new resonances, intensity changes, and line-width broadenings. Kinetic analysis of the curing data gave different kinetic parameters for the two cure temperatures, which is expected since the first cure temperature is below the material's glass transition temperature (Tg) while the second cure temperature is above the Tg.
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Russell et al. (1998) studied this question.