Odd-even effects and the influence of length and specific positioning of alkoxy side chains on the optical properties of PPE-PPV polymers

This contribution reports the combined influences of odd−even effects and the specific positioning of alkoxy side chains OR1 = (OCn+10H2(n+10)+1) and OR2 = (OCnH2n+1) (with n = 6, 7, 8, 9) on the phenylene−ethynylene and phenylene−vinylene segments, respectively, on the optical properties of hybrid polymers P(n+10)/n of general repeating unit:  −Ph−C⋮C−Ph−C⋮C−Ph−CHCH−Ph−CHCH−. For the polymeric materials, visual color impression varies alternatively between orange red (P16/6 and P18/8) and yellow (P17/7 and P19/9) according to the odd and even features of the alkoxy side chains, where odd or even relates to the total number of sp3-hybridized atoms within the side chains. This side chain related effect is ascribed to both absorptive and emissive behaviors of the polymers on the basis of photophysical investigations in the bulk. Almost identical thin film absorption spectra were obtained for all four materials; however, the photoluminescence of the odd polymers, P16/6 (λf = 556 nm) and P18/8 (λf = 614 nm), ...