Two-photon absorption property of a conjugated polymer: influence of solvent and concentration on its property.

The Suzuki coupling reaction was utilized to prepare target conjugated polymer P1, whose main chain consists of 3,5-dicyanopyridine moieties as electron acceptors and both triphenylamino groups and fluorene moieties as donors. This polymer exhibits excellent solubility in organic solvents and high thermal stability (5% of weight loss at 398 degrees C). Detailed spectroscopic studies including absorption and fluorescence emission in solvents of different polarity were also conducted. The influence of the solvent and concentration on its two-photon absorption (TPA) property was studied by a two-photon-induced fluorescence (TPIF) method. It was found that the highest two-photon absorption cross section (13,260 GM at a laser wavelength of 940 nm) appeared in 1,2-dichloroethane, a solvent with a moderate polarity. Meanwhile, with the increase of its concentration in chloroform, its TPA cross section value is reduced, implying that its two-photon absorption process in its chloroform solution is not a pure intrachain process.