Abstract:

Polyaluminocarbosilanes(PACS) with different Al contents were synthesized by reacting liquid polycarbosilane(LPCS) with aluminum acetylacetonate[Al(AcAc)₃]. Compared with those reported in literatures, this route is considered to be more convenient and safer since no circulating reflux is needed. It was shown that the composition and structure of LPCS heated and kept at the synthesis temperature of PACS remained fairly stable. The chemical elemental analysis results of PACS indicated that through this route the Al contents were almost fully introduced into PACS from Al(AcAc)₃, and with the increasing of Al contents, the O contents also increased. Furthermore, the formation of AlO₄, AlO₅ and AlO₆ was confirmed by ²⁷Al MAS NMR results. On the base of the structure analysis it was suggested that LPCS reacted with Al(AcAc)₃ by consuming Si—H bonds. Then Si—O—Al crosslinking bonds were formed, leading to the increases of the number average molecular weight and the polydispersion index in molecular weight with the increase of Al contents in PACS.

Key words: Liquid polycarbosilane; Polyaluminocarbosilane; Aluminum acetylacetonate; Elemental analysis; Structure characterization