Method for preparing polyaluminocarbosilane

Polyaluminocarbosilane (PACS) was synthesized directly by the one-pot reaction of polydimethylsilane (PDMS) with aluminum acetylacetonate [Al(acac)₃] in an autoclave. In this closed system, all the aluminum in Al(acac)₃ was converted into PACS. Therefore, the content of aluminum, could be readily controlled quantitatively. On the basis of Fourier transform infrared, ¹H-NMR, ¹³C-NMR, ²⁹Si-NMR, and ²⁷Al magic-angle spinning NMR analysis, the reaction mechanism was proposed as follows: PDMS dissociated during pyrolysis to generate silicon free radicals, and then they reacted with Al(acac)₃ to yield PACS containing (Si-O)_nAl groups (n = 4, 5, or 6). Meanwhile, these reactions resulted in the cleavage of O-C and/or O=C bonds in Al(acac) ₃. Some of the free-radical fragments generated by this cleavage continued to react with the silicon free radicals and were incorporated into the structural units of PACS; the rest of them may have been converted into small oxygen-containing compounds, which were removed in the subsequent processing after the reactions.