Synthesis and characterization of hyperbranched polycarbosilazane

In order to enhance the reactivity of the silyl-containing ceramic precursor, a hyperbranched silyl-containing polymer with low viscosity and plenty of terminal vinyl-groups was prepared. A novel AB₄ type monomer, bis(N, N-diallylamino)methylsilane, was synthesized first by aminolysis of MeHSiCl₂ and then was polymerized via hydrosilylation reaction using H₂PtCl₆ as the catalyst. The polymerization process was monitored by FT-IR spectroscopy. The polymer product was purified via precipitation using ethyl ether and acetonitrile and was analysed by using ¹H-NMR, ²⁹Si-NMR and FT-IR spectroscopy. The results indicated that the polymer was hyperbranched polycarbosilazane, and α-hydrosilylation was the main reaction. The degree of branching (DB) of the hyperbranched polymer was 0.56 calculated from the Si-NMR spectrum, and the average molecular weight (M_w) was 13 580 g/mol determined by light scattering method. It was found that there still existed a lot of functional vinyl end groups, which can be used as promising reaction centers for curing or modification of the polycarbosilazane.