Polysilane polymers photochemistry

Within these main categories a number of subdivisions will generally be found, usually based on the nature of the groups attached to silicon. The emphasis in the subject matter is chiefly in terms of the chemical transformations effected by the radiation, and little emphasis is placed on the photochemical mechanisms involved, which are dealt with in an accompanying chapter of this treatise. Also, the photochemistry of high molecnlar weight polysilane polymers, or of polymers containing silicon as part of the backbone of the molecules, is not dealt with in this chapter, but some relevant material will be found in other chapters in this volume. 

In summary, the production of substituted silylenes and silyl radicals upon exhaustive irradiation at 254 nm of polysilane high polymers suggested that the polymer photochemistry resembled that previously reported for short chain acyclic and cyclic oligomers (39). More recent experiments, however, have suggested that the photochemical mechanism for the degradation of the high polymers is more complex than first envisioned (vide infra) (48). 

Polysilanes absorb electromagnetic energy and undergo chain scission. This is an extremely important property of these polymers in terms of applications, Photochemistry is exhibited both in solution and in the solid slate. 

Polysilane high polymers possessing fully saturated all-silicon backbone have attracted remarkable attention recently because of their unique optoelectronic properties and their importance in possible applications as photoresists, photoconductors, polymerization initiators, nonlinear optical materials etc. A number of review articles have been published on this topic4-9. The studies in this field have stimulated both experimental and theoretical chemists to elaborate on understanding the excited state nature of polysilanes and oligosilanes and of their mechanistic photochemistry. 

Several comprehensive reviews on the preparation, structure, properties, photochemistry, and redistribution of polysilanes prepared by the Wurtz coupling method have been published.1516 31 33 There are also several excellent reviews on the transition-metal-complex-catalyzed dehydrocoupling of hydrosilanes to polysilanes.34 36 The present section reviews the more recent work on the dehydropolymerization of hydrosilanes to polysilanes, catalyzed by transition-metal complexes under homogeneous conditions. Extensions of the methodology to the dehydropolymerization of hydrogermanes, hydrostannanes, and hydrophosphanes to the corresponding polymers are also reviewed. The literature is covered up to early 1997. 

Polysilane derivatives constitute a new class of radiation-sensitive materials with interesting physical and electronic properties. The photochemical decomposition of polymers containing disilanyl units seems adequately explained by silicon-silicon bond homolysis and subsequent radical reactions. The solution photochemistry of longer silicon catenates results in the extrusion of substituted monomeric silylenes, as well as the formation of silyl radicals produced by chain homolysis. Recent studies indicating that the... 

Miller RD, Willson CG, WaUroff GM, Clecak N, Sooriyakumaran R, Michl J, Karatsu T, McKinley AJ, Klingensmith KA, Downing J (1989) Polysilanes photochemistry and deep-UV lithography. Polym Eng Sci 29(13) 882-886... 

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