Disilane unit-fused poly (diphenylamine) (poly(10, 11-dihydro-10,11-disila-5,10, 10,11,11-pentamethyl-5H-dibenz[b,f]azepine-2,8-diyl), PDSiAzep) were prepared and properties of these compounds were studied. Oxidation of PDSiAzep led to related disiloxane-fused poly(diphenylamine) (poly(5,7-disila-6-oxa-5,5,7,7,12-pentamethyl-5,6,7,12-tetrahydrodibenz[b,g]azocine-3,9-diyl) PSiO). These polymers have new heterocyclic unit. Not only UV and Cyclic voltammetry (CV) measurements but also X-ray crystallography of the related dibromide suggested that the structure of the bridging unit affected pi-conjugation through the N atom. The highest conductivities of electrochemically doped PDSiAzep and PSiO were 2.0 x 10(-4) and 1.3 x 10(-2), respectively. Turn-on bias voltage of a double layer electroluminescent device comprising PDSiAzep was higher than that of PSiO. These electrical properties were depended on effective a-conjugation through the N atom.