Deprotection-free preparation of propargyl ether-containing phosphinated benzoxazine and the structure-property relationship of the resulting thermosets

Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether-containing benzoxazines. In this study, we report a facile, deprotection-free preparation of a propargyl ether-containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH-containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high-resolution mass spectrum, 1H, 13C, 1H-1H, 1H-13C nuclear magnetic resonance (NMR) spectra, and X-ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring-opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structureproperty relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 degrees C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/degrees C, and Td 5% (N2) is 393 degrees C, respectively, which are higher than those of the homopolymer of (1). Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012