Quantitative determinations in the molecular structures of polyaluminocarbosilane

The molecular structure of polyaluminocarbosilane (PACS) derived from polycarbosilane (PCS) was investigated by 1H, 29Si, 27Al NMR and elemental analyses. Quantitative methods based on experimental data were established to determine the exact amounts of O-containing groups, namely Si−O−Al and Si−O−Si, and the relative numbers of linear and cyclic Si−C segments in PACS. The HSiC2O groups and the SiH/SiH2 in linear Si−C segments, single and condensed six-member Si−C rings were quantitatively distinguished. The results showed that PACS molecules consisted predominantly of single six-member Si−C rings. The introduction of Al into PCS led to H consumption through which Al was closely bonded to O by breaking Si−H or Si−CH3 to form Si−O−Al cross-linking bonds and AlOx (x = 4–6) groups in PACS. The AlOx (x = 4–6) groups acted as linkage centers to bridge smaller PCS molecules through which the molecular weight and its distribution coefficient of PACS were both apparently increased.