Two-photon absorption properties of hyperbranched conjugated polymers with triphenylamine as the core

Two new hyperbranched phenylene vinylenes (HPVs) with triphenylamine as the core, 2,5-dihexyloxyl substituted phenylene vinylene as the connecting unit, and electron-donating triphenylamine or electron-deficient nitrobenzene as the different terminal groups were synthesized by modified Wittig polymerization reaction. Their one- and two-photon absorption (TPA) properties have been investigated. The two-photon absorption cross sections of the two polymers were performed by open-aperture Z-scan experiment using 120 femtosecond (fs) pulse, and their TPA cross section were determined to be 1.43 and 0.64×10−20 cm4/GW per repeating unit at 800 nm, respectively. In chloroform, HPVs exhibit intense frequency up-converted fluorescence under the excitation of 120 fs pulses at 800 nm with the peaks located at 544 and 554 nm, respectively.