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Polymeric precursors to Si/C/N-ceramics can be obtained by thermal crosslinking of polysilazanes. The precursor is then pyrolysed at a temperature of 1000 °C into the amorphous ceramic. Between 1000 and 2000 °C this amorphous state is transformed into the thermodynamically stable phases. The processes during pyrolysis and crystallization are connected with microstructural conversion. Simultaneously, changes of chemical and physical properties take place. The successive conversion of the atomic coordination during the transformation from the polymer into the amorphous ceramic and finally into the crystalline ceramic was studied using solid-state NMR. 29 Si-, 13 C- and 1 H-spectra were recorded. The result is a detailed report of the reactions and changes in structure occuring during ceramization of a polyhydridomethylsilazane and crystallization of its ceramic residue. Furthermore, the amorphous state of this material was compared with a polyvinylsilazane-derived amorphous ceramic.

Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra have been obtained for annealed films of poly (p-phenylene vinylene) (PPV), prepared through the precursor route and for a deuterated PPV-d4, poly (p-2,3,5,6 tetradeuterophenylene vinylene). 13C CPMAS spectra of PPV are of high resolution, typically characteristic of a nearly fully crystalline structure. All four phenylene and vinylene resonances have been assigned, and for stretched films the 13C CPMAS linewidth and the quality of crystallinity are independent of the draw ratio. 13C CPMAS resolution and crystallite size (as determined by transmission electron microscopy, TEM) depend upon final annealing temperature. The greatest NMR resolution and largest crystallite size are obtained for films annealed at 300°C. The 13C CPMAS NMR spectra show the presence of phenylene ring 180° rotational jumps, and 13C CPMAS resolution is affected by rotational disorder about phenylene-vinylene bonds. NMR data show that PPV films possess molecular motion at elevated temperatures. Enhancement of this motion during annealing may provide a means for improving the quality of PPV crystallinity.