Characterization of poly(di-n-hexylsilane) in the solid state II. (13)C and (29)Si magic angle spinning NMR studies.

We report the (13)C and (29)Si magic angle spinning NMR spectra of poly(di-n-hexylsilane) in the solid state. The spectra are interpreted in terms of two co-existing phases: a rigid phase (termed Phase I) in which the silicon backbone and the hexyl side-chains are believed to be in a predominantly trans conformation; and a more mobile phase (termed Phase II) in which both the (13)C and (29)Si resonances are more shielded, reflecting the introduction of gauche bonds into both the backbone and side-chains. There is a transition at 42C above which Phase I is absent, in agreement with X-ray results. The (13)C resonances of Phase I show a 1:1 splitting which cannot be fully interpreted at present but is believed to arise from two modes of side-chain packing of nearly equal populations in slow exchange.