Solid-state nuclear magnetic resonance (NMR): Application to precursors of ceramics?Polycarbosilane

Abstract

The chemical structures of oxidation- and electron irradiation-cured polycarbosilane fibers has been studied by IR and chemical analysis, but its structure has not been identified in detail. In this work, the chemical structure and curing mechanism was examined by solid-state high-resolution NMR spectroscopy. From the analysis of NMR spectra, it is explained that (i) in oxidation curing of PCS fibers, oxygen attacks first the SiC3H bond and forms the SiC3O bond and, next, the SiC4 backbone bond and forms the SiC2O2 units; (ii) in electron irradiation curing, the signal intensity of SiC3H units decreases with the increase in dose, the increase in the signal being due to the formation of SiC4 units; (iii) solid-state29Si high-resolution (CP/MAS) NMR spectroscopy is a powerful tool for investigating the chemical structure and curing mechanism of PCS fibers complementing infrared and solid-state13C high-resolution NMR spectroscopy; and (iv)1H CRAMPS NMR spectroscopy is very useful for investigating the chemical structure and curing mechanism of PCS fibers.