Four main-chain type polybenzoxazine precursors were synthesized from the Mannich-type polycondensation of biphenol A, paraformaldehyde, and four typical aromatic diamines: 1,4-phenylenediamine, 4,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl ether, and 2,2-bis[4-(4-aminophenoxy)phenyl] propane. The solvent effect on the polycondensation was examined. We found that polybenzoxazine precursors prepared in toluene/ethanol exhibit higher purity, higher molecular weight, and lead to better thermal properties after curing than those prepared in chloroform, as recommended by Takeichi's group (T. Takeichi et al., Polymer, 2005, 46, 12172). The cured polybenzoxazine films prepared by these polybenzoxazine precursors display unusual flexibility, extremely high T-g, and low surface energy. They show T-g values as high as 272-353 degrees C (DMA data), coefficients of thermal expansion as low as 39-49 ppm/degrees C, contact angles as high as 100-102 degrees, and surface energy as low as 17.7-24.5 mJ m(-2)

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Three fluorinated benzoxazines (14–16), which cannot be synthesized by the traditional one‐step approaches, were synthesized by a three‐step procedure using fluorinated aromatic diamines (2–4) as starting materials. The structures of the monomers were confirmed by 1H NMR, IR, and high‐resolution mass spectra. The low dielectric thermosets, P(14–16), were prepared by ring‐opening of (14–16). IR analysis was utilized to monitor the ring‐opening reaction of (14–16) and to propose the structures of P(14–16). The thermal and dielectric properties of P(14–16) were studied and compared with a nonfluorinated polybenzoxazine P(13), which is derived form the ring‐opening of 2,2‐bis(4‐aminophenoxy)phenyl)propane (1). Besides, the structure–property relationship of the P(13–16) is discussed. According to Tg measurement, the ortho‐positioned CF3 substituents impart greater steric hindrance for ring‐opening of benzoxazines than CF3 substituents of hexafluoropropane. Incorporating a biphenol F‐based benzoxazine, (F‐a), into fluorinated benzoxazines (15–16) can dilute the effect of ortho‐positioned CF3 substituents on steric hindrance, leading to a higher crosslinking density and consequently a higher Tg. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4970–4983, 2008

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Three aromatic diamine‐based benzoxazines were successfully prepared by a facile, clean, one‐pot procedure from 1,4‐phenylenediamine (1), 4,4′‐diaminodiphenyl ether (2), and 4,4′‐diaminodiphenyl methane (3), respectively. Their structures were confirmed by NMR spectra and single crystal diffractogram. The effect of the reactivity of diamines on the purity of the resultant benzoxazines was discussed. The resultant benzoxazines were applied as hardeners for cresol novolac epoxy (CNE). The processing window, the latent curing characteristic, and the miscibility of benzoxazine/CNE systems were discussed. Compared with diamines (1 and 3), (1 and 3)‐based benzoxazines show latent curing characteristic as epoxy hardeners, and wide processing windows can be obtained. Compared with diamine (2) which is immiscible with CNE in the molten state, (2)‐based benzoxazine shows good miscibility with CNE. Dynamic mechanical analysis shows the Tgs of the benzoxazine/CNE thermosets are as high as 242–243 °C. Thermogravimetric analysis shows the outstanding thermal stability of the resultant thermosets. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2430–2437, 2010