Silicon-29 NMR Spectroscopy

The fused silicate route to protoimogolite and imogolite

“…Naively it may have been believed that these three methods might form the same intermediate silicic acid in the formation of imogolite. However silicic acid structure depends on the way it is prepared [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Elsewhere [14] we have followed the formation of protoimogolite and then imogolite from hydrolyzed solutions of tetraethoxysilane.…”

Liquid polycarbosilane-derived C/C–SiC composites with improved mechanical strength for high temperature applications

“…In the 13 C NMR spectrum of LPCS, resonance peaks corresponding to Si-CH 3 and Si-CH 2 -Si are observed in the region À 5 to 20 ppm. Multiple resonance peaks observed in the region 20-42 ppm are due to the presence of Si-CH 2 -O-Si groups and cyclic oligomers in different stereochemical environments [10]. In the 29 Si NMR spectrum (Fig.…”

Silicon-29 NMR

“…West and Stanislawski used a similar approach [equation (5)] to explain the shifts of oligomeric permethylsilanes:…”

“…δ Si(k) = B + A l n kl (5) where the constant B is 8.5 ppm and A l represents the influence of silicon atoms in the α (−28.5 ± 0.10 ppm), β (+3.9 ± 0.05 ppm), γ (+1.2 ± 0.09 ppm), and δ positions (+0.2 ± 0.01 ppm) relative to the silicon atom considered, and n kl the incidence of A l . Substituent parameters for fluorine or chlorine could also be calculated.…”