Study on synthesis and the reaction mechanism of polybenzoxazine-silica nanocomposites provided from perhydropolysilazane

Abstract

Abstract Polybenzoxazine/silica nanocomposites were synthesized with perhydropolysilazane (PHPS) and benzoxazines via thermal polymerization in one step. The reaction of benzoxazine's hydroxy group and PHPS was investigated via 1H nuclear magnetic resonance and Fourier transform infrared spectrometry. At low heating temperatures, benzoxazine was converted to a polymer with a N,O-acetal structure, whereas at high heating temperatures, it was converted to a polymer with a Mannich structure because high temperatures allow the polymer to react with the Si H groups of PHPS. Measurements of synthesized poly[6,6′-(1-methylethylidene)bis(3,4-dihydro-3-2H-1,3-benzoxazine)](PB-a)/silica nanocomposites showed that no reaction between PB-a hydroxy groups and PHPS Si H groups occurred because of a stepwise heating process. Measurements of synthesized poly[6,6′-(1methylethylidene)bis(3,4-dihydro-3-2H-1,3-hexylbenzoxazine)] (PB-hda)/silica nanocomposites showed that no competitive reaction between PB-hda and PHPS occurred when materials were heated at 160 °C for 1 h because PB-hda formed no hydroxy group. Conversely, at 240 °C, a competitive reaction between PB-hda and PHPS occurred, which led to the formation of Si O C linkages.