LAUSR

High-molecular-weight (HMW) benzoxazines were synthesized by Mannich condensation with various combinations of bisphenols and diamines, and the mechanical and thermal properties of the polybenzoxazines derived from the HMW benzoxazines were measured by tensile tests and thermogravimetric analysis (TGA) to investigate the structure-property relationship. Free-standing precursor films were easily obtained from the solutions of HMW benzoxazines by a cast method on glass plates, and transparent and very tough polybenzoxazine films were obtained by thermally curing the precursor films at a temperature up to 240 °C. The polybenzoxazine films showed higher tensile strength and larger elongation at break than typical polybenzoxazine, i.e., PB-a obtained from low-molecular weight benzoxazine synthesized from bisphenol-A and aniline. In particular, among the HMW polybenzoxazines presented in this work, the PODP-oda film derived from 4,4′-oxydiphenol and 4,4′-oxydianiline showed remarkably good mechanical properties (E = 3.7 GPa, sb = 125 MPa, and eb = 4.5%). Moreover, the PODP-oda film revealed a higher 5 wt% weight loss temperature (Td5 = 332 °C) and char yield at 850 °C (CY850 = 58%) than PB-a (Td5 = 301 °C and CY850 = 42%), as evidenced by TGA, suggesting good thermal stability. High-molecular-weight (HMW) benzoxazines were synthesized by Mannich condensation with various combinations of bisphenols and diamines, and the mechanical and thermal properties of the polybenzoxazines derived from the HMW benzoxazines were measured by tensile tests and thermogravimetric analysis to investigate the structure-property relationship. Among the polybenzoxazines presented in this work, the PODP-oda film derived from 4,4′-oxydiphenol and 4,4′-oxydianiline showed remarkably good mechanical properties (E = 3.7 GPa, sb = 125 MPa, and eb = 4.5%) and thermal stability (Td5 = 332 °C).