Abstract: Hyperbranched polycarbosilazane P1 was successfully prepared from AB₄ type monomer bis(N,N-diallylamino)methylsilane via fast hydrosilylation initiated by ultraviolet(UV) irradiation, with bis(acetylacetonato)platinum(Ⅱ) as the catalyst. For comparison, hyperbranched polycarbosilazane P2 was also prepared with the same monomer via heating-initiated polymerization at 80 ℃ with Karstedt's catalyst. The structures of the resulting polymers were well characterized by FTIR, ¹H NMR, ¹³C NMR, ²⁹Si NMR and size exclusion chromatography/multi-angle laser light scattering(SEC/MALLS) technology. By IR monitoring, it was found that polyhydrosilylation initiated by UV irradiation was much faster than that initiated by heating. NMR analyses confirmed that the resulting polymer possessed a hyperbranched architecture, indicating that α-hydrosilylation may mainly occur during UV-initiated polymerization. Degree of branching(DB) and average number of branches(ANB) of P1 were determined via ²⁹Si NMR and were found to be 0.46 and 0.53, which were close to the theoretical values, respectively. And the weight average molecular weight, polydispersity index and exponent for Mark-Houwink equation of P1 were determined to be 12500 g/mol, 2.1 and 0.44, respectively, which were similar to those of P2.

Key words: Ultraviolet, Hydrosilylation addition reaction, Hyperbranching, Polycarbosilazane