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 29Si—NMR spectrum

and the average molecular weight(M)was 13 580 g／mol determined by fight scattering method．It was found that there still existed a lot offunctional vinyl end groups

which can be used as promising reaction centers for curing or modification of the polycarbosilazane．