A new monomer

vinyltriallylsilane(CB3)

having functionnal groups with different hydrosilylation reactivity was designed and synthesized by allylation reaction from vinyltrichlorosilane．Then

photocrosslinkable hyperbranched poly(siloxysilane)with terminal allyl groups was prepared via hydrosilylation reaction of vinyltriallylsilane(CB3)and dimetbylbis(dimethylsiloxy)silane(A2)monomers at the presence of Karstedt catalyst

and characterized by means of FTIR

1H—NMR

29Si—NMR

and SEC／RI／MALLS technology．The polymerization process of A2 and CB3monomers Was studied in situ by using FTIR．It was found that silicon hydride would preferentially react with vinyl groups during the reaction．This can cause to the generation of an intermediate with one Si—H and three allyl groups．By using it to conduct fuaher self-polymerization

hyperbranehed polymer can be obtained．The degree of branching of the resuhing hyperbranched poly(siloxysilane)was calculated to be 0．44 by quantitative29 Si—NMR spectroscopy．and the weight average molecular weisht was l2．1 kg／mol with its polydispersity of 2．52．Finally．the UV curing behavior of the resulting polymer initiated with different photoinitors was also investigated．