Polysilylenes

Polysilanes (or polysilylenes) consist of a silicon-catenated backbone with two substituents on each silicon atom. The two groups attached to the silicon chain... 

The history and development of polysilane chemistry is described. The polysilanes (polysilylenes) are linear polymers based on chains of silicon atoms, which show unique properties resulting from easy delocalization of sigma electrons in the silicon-silicon bonds. Polysilanes may be useful as precursors to silicon carbide ceramics, as photoresists in microelectronics, as photoinitiators for radical reactions, and as photoconductors. 

Matyjaszewski Krzysztof, Dorota Gresta, Hrkach Jeffrey S, Hwan Kyu Kim (1995) Sono-chemical synthesis of polysilylenes by reductive coupling of disubstituted dichlorosilanes with alkali metals. Macromolecules 28 59-72... 

Polysilylenes have been widely investigated in the past decade because of their potential applications in the field of materials science [1], Recent applications of polysilylenes in SiC precursors [2], microlithography [3], photoinitiators [4], and reprography [5] show that polysilylenes are very promising as advanced materials for high technology of the next generation. 

In order to avoid the SET process, we chose diphenylmethylsilyl anions (PI MeSiM 8a, M = K 8b, M = Na 8c, M = Li) as initiators for 7 instead of alkyllithium and benzene as a solvent. The polymerization did not take place in benzene with silyl anions alone. However, in the presence of an equimolar amount of suitable cryptands, the silyl anions initiated the polymerization. The results are summarized in Table 2. The molecular weights of polysilylenes thus obtained were in good agreement with the calculated values within experimental error. 

Polysilanes (or polysilylenes) consist of a silicon-catenated backbone with two substituents on each silicon atom (Structure 1). The groups R and R attached to the silicon chain can be of a large variety. Polysilanes with alkyl and/or aryl substituents have been the most thoroughly investigated [1-3], whereas polysilanes having at least a heteroatom substitution such as H, Cl, OR, NR2 have received much less attention [4]. The number of silicon atoms is usually from several hundreds to several thousands. 

The polysilanes oi polysilylenes (25), an unusual class of inorganic polymers, saw a very intense period of investigation during the 1980s. 

Polysilylenes and polygermylenes (also described as polysilanes and poly-germanes) are linear a-bonded Si or Ge polymers that contain a variety of C-based pendant groups. For charge transport, the role of the pendants is secondary and transport occurs by hopping between ordered main-chain segments between 15 to 30 repeat units separated by disordered links (Abkowitz and Stolka, 1988, 1988a, 1996). 

Kepler et al. (1983, 1984, 1987) measured hole mobilities of poly(methyl-phenylsilylene) (PMPS). The mobilities were field dependent and thermally activated with an activation energy of 0.24 eV. The transport was nondispersive at room temperature. With decreasing temperature, however, the transients become increasingly dispersive. Because the same mobility was observed in a wide range of alkyl-substituted polysilylenes, Kepler et al. argued that hole transport occurs through the conjugated states of the chain backbone. 

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