Formation,Characterization, and Stability of Novel Aluminocarbosilazane Macromolecules

Abstract

A novel class of polycarbosilazane?AlCl₃ macromolecules (AlCSZ) with a Si/Al molar ratio of 1 : 1, 2 : 1, and 3 : 1 were prepared by a two‐step reaction, formation of H₂NCH₂CH₂NH₂?AlCl₃ adducts followed by condensation of H₂NCH₂CH₂NH₂ with (CH₃)₂SiCl₂ in an aprotic solvent containing triethylamine base. The resulting AlCSZ materials were examined by elemental analysis, infrared spectroscopy (FT‐IR), mass spectrometry (MS), and powder x‐ray diffraction (XRD). The average polycarbosilazane chain–chain distances in the aluminum‐free polycarbosilazane and these AlCSZ macromolecules were estimated from the XRD data and found to be 5.94, 6.75, 6.88, and 7.19 Å, respectively. This demonstrates that AlCl₃ is incorporated between the polycarbosilzane chains and has caused chain–chain expansion. The thermal properties of these AlCSZs were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). They are air stable white solids but decompose in water forming the corresponding dimethylsiloxane, ethylenediamine, and aluminum oxide.