Three new PPV derivatives with dialkoxyphenyl substituents, BEH2P−PPV, BEH3P−PPV, and BEH4P−PPV have been synthesized. The polymers were characterized by FT-IR, 1H NMR, and elemental analysis. The polymers possess excellent solubility, high molecular weights, high photoluminescence efficiencies and good thermal stability. The influence of substitution pattern on the formation of structural defects has been investigated by measuring the signal due to tolane−bisbenzyl moieties (TBB) in the proton NMR spectra. BEH2P−PPV with a steric phenyl group at the ortho-position on the side phenyl ring shows the lowest amount of TBB, which indicates suitable steric hindrance can be applied to suppress the formation of irregular head-to-head and tail-to-tail linkage in the polymer chains. In addition, the polarity of solvents used for the Gilch polymerization will also affect the amount of irregular structure in the polymers. Polar solvents such as THF will result in polymers with low TBB content. Energy level measureme...