Three aromatic diamine-based, phosphinated benzoxazines (7-9) were prepared from three typical aromatic diamines-4,4'-diamino diphenyl methane (1), 4,4'-diamino diphenyl sulfone (2), and 4,4'-diamino diphenyl ether (3) by a one-pot procedure. To clarify the reaction mechanism, a two-pot procedure was applied, in which the reaction intermediates (4-6) were isolated for characterization. The structures of intermediates and benzoxazines were confirmed by high resolution mass, IR, and 1D and 2D-NMR spectra. In addition to self-polymerization, (7-9) were copolymerized with cresol novolac epoxy (CNE). After curing, the homopolymers of P(7-9) are brittle while the copolymers of (7-9)/CNE are tough. Dynamic mechanical analysis shows the T(g)s of (7-9)/CNE copolymers are 187, 190, and 171 degrees C, respectively. Thermal mechanical analysis shows the CTEs of (7-9)/CNE copolymers are 46, 38, and 46 ppm, respectively. All the (7-9)/CNE copolymers belong to an UL-94 V-0 grade, demonstrating good flame retardancy. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4555-4566, 2010