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Poly [4,4'-(tetramethyldisilanylene)biphenylylene] (la), poly [4,4'-(tetraethyldisilanylene)biphenylylene] (lb), and poly[4,4'-( 1,2-dimethyl-1,2-diphenyldisilanylene)biphenylylene] (lc) were prepared by the condensation reaction of the respective 4,4'-bis(chlorosilyl)biphenyls with sodium. Poly[4,biphenylylene] (Id), poly [4,4'-(methylphenylsilylene)biphenylylene] (le), and poly[3,3'-(dimethylsilylene)biphenylylene] (If) were obtained from the nickel-catalyzed dehalogenative coupling of the products formed from the reaction of the respective bis(bromophenyl)-substituted silanes with magnesium. Poly[(disilanylene)terphenylylenes] 2a-c and poly[(disilanylene)quaterphenylylenes] 3a-c were also synthesized by the similar nickel-catalyzed dehalogenative coupling reactions of di-Grignard reagents prepared from the respective bis(4-bromophenyl)-substituted disilanes, with p-dibromobenzene and 4,4'-dibromobiphenyl, respectively. The disilanylene-substituted polymers la-c, 2a-c, and 3a-c were found to be photoactive. Irradiation of the thin solid films prepared from these polymers in air resulted in scission of the Si-Si bonds, leading to the formation of degradation products including silanol and siloxy units. Poly[(silylene)biphenylylenes] Id-f were found to be inert toward UV irradiation. Photochemical behavior of the disilanylene-substituted polymers was also investigated in solution, and photoactivities of these polymers were found to decrease with increasing the degree of an extension of the -electron system. The results of crystal orbital calculations for poly[(disilanylene)oligophenylylenes] have also been reported.

found to be 7800-35 OOO by gel-permeation chromatography relative to polystyrene standards. The photochemical properties of the polymers (4a-4d) having silylene and disilanylene units were investigated. Only poly[5,5'-(1,2-dimethyl-l,2-diphenyldisilanylene)-2,2'-dithienylene] (4d) was found to be photoactive, but the others were inactive. When the thin solid films prepared from the polymers 4a-4e by spin-coating were exposed to antimony(V) fluoride in uacuo, the films became conducting; their conductivities were determined to be 10-2-10-3 S cm-' by the four-probe method.

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