trans-Poly(dimethylsilylenearylenevinylene)s (trans-rich) and cis-poly-(dimethylsilylenearylenevinylene)s (cis-rich) containing phenylene, biphenylene, and phenylenesilylenephenylene units were prepared by hydrosilylation catalyzed with the RhI(PPh3)(3) complex. The addition of a phenylene pi unit to poly(silylenephenylenevinylene) expanded the conjugation in the main chain, whereas the insertion of a dimethylsilylene sigma unit in the biphenylene moiety reduced the conjugation. UV spectra of the trans-type polymers showed redshifts and hyperchromic effects with respect to those of the cis-type polymers, indicating wider conjugation, and the quantum yields of emission of the former polymers were much higher than those of the latter polymers. The quantum yield of the trans-rich polymer with the biphenylene moiety reached 0.15, which was about 10(2) times as large as those of trans-type polymers with phenylene (3.4 x 10(-3)) and phenylenesilylenephenylene (1.9 x 10(-3)) moieties. The effects of the geometric structure and pi unit on the absorption and emission properties of these polymers were examined with molecular orbital methods.