Theoretical investigation on the effects of π-conjugation attenuation of poly(p-phenylenevinylene) polymers upon incorporating 2,2′-bipyridines

Localized-density-matrix method [Yokojima and Chen, Phys. Rev. B 59 (1999) 7259] has been employed to calculate the optical absorption of poly(p-phenylenevinylene) incorporated with 2,2′-bipyridines. The poly(2,5-bis(2′-ethylhexyloxy)-1,4-phenylenevinylene) (Behppv) as well as Polymer 1 and Polymer 2 whose 2,2′-bipyridyl-5-vinylene unit incorporated with one and three 2,5-bis(n-decyloxy)-1,4-phenylenevinylene monomer units, respectively, have been studied. The calculated results are consistent with the experimental results [Chen et al., J. Phys. Chem. A 103 (1999) 4341]. Moreover, the density matrices corresponding to first absorption peak for each of three polymers are examined and the microscopic origin of energy shifts is determined.