Disilane backbone polymers

Ishikawa and co-workers (50, 51) have also reported the photodegradation of backbone disilane polymers (Scheme III). In this case, as in the previous example with pendant silyl substituents, silicon-silicon bond homolysis to produce silyl radicals was the predominant process. When irradiated in toluene, the photodegraded polymer showed a substantial -SiH band at 2150 cm in the IR spectrum. Similarly, NMR spectroscopic examination of the irradiated polymer showed evidence of silyl radical substitution into the solvent toluene. Irradiation of the polymeric disilane in deuterated methanol produced no bands due to Si-D in the IR spectrum and resulted in the incorporation of the elements of methanol into the chain ends (as revealed by NMR spectroscopy). For the phenyl-substituted polymer, the NMR evidence indicated that <5% of rearranged cyclohexadiene derivatives were formed. 

Lewis acids, such as triphenylboron, dissolved in the starting disilane, prevent branching of the polymer backbone during the reaction course. 

Polycarbosilanes are polymers in which organosilicon moieties as silanes, disilanes, and trisilanes and carbon as aliphatic or aromatic units lie in the polymer backbone. The general formula for this class of material may be represented by structure 33. Polycarbosilanes may be linear, cyclic, polycyclic, extended networks, or any combination thereof R and R are the usual substituents found in organo-silanes, and (C) represents difimctional aliphatic (saturated or unsaturated) or aromatic groups that can serve as bridges between the silicon moieties. Consequently, a... 

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