Three hyperbranehed poly(siloxysilanes)were prepared from AB3-type monomers at the presence of Karstedt catalyst．The detailed synthesis procedures of AB3-type monomers by reaction between γ-methacryloyloxy propyltrimethoxysilane or vinyltrimethoxysilane with chlorosilane using anhydrous ferric chloride as the catalyst were described．This new approach can simplify the synthetic routes for hyperbranched polysiloxanes．FTIR

1H-NMR

13C-NMR

29Si—NMR

elemental analysis and SEC／MALLS were employed to identify the structure of the polymers．The analyses revealed that the reaction between alkoxysilane and chlomsilane could be feasibly catalyzed by anhydrous ferric chloride．The reaction of vinyltrimethoxysilane with chlorsilane could be carried out more easily than that of γ—methylacrycyloxypropyltimethoxylsilane with chlorosilane due to its steric hindrance effect．