Structure and segmental motions in symmetrically substituted poly(ferrocenylsilanes): A carbon-13 CPMAS NMR contact time study

The structure and thermal behavior of two organometallic polymers, poly(fer rocenyl dimethylsilane) (I) and poly(ferrocenyl di-n-butylsilane) (II), hav e been examined using a variety of physical characterization methods which reveal differences in their crystalline structures and associated segmental librations. In addition to examination with differential scanning calorime try and wide-angle X-ray scattering, solid-state C-13 NMR spectra were acqu ired for a wide range of H-1-C-13 contact times. The spectra of I at room t emperature exhibit two isotropic chemical shifts for the methyl groups, ind icating the presence of different environments. The initial cross-polarizat ion (CP) times of crystalline, protonated carbons are interpreted with refe rence to values found in the literature. The main chains of both polymers w ere found to be fairly rigid on the time scale of T-CH, but the side chains of II are very disordered. The relevance of the C-13 measurements at room temperature is discussed with regard to a higher temperature transition ind icated in the DSC trace of II.