Synthesis, optical and initiating properties of new two-photon polymerization initiators: 2,7-Bis(styryl)anthraquinone derivatives

C2v symmetrical anthraquinone derivatives, 2,7-bis(2-(4-dimethylamino-phenyl)-vinyl)anthraquinone (1) and 2,7-bis(2-(4-methoxy-phenyl)-vinyl)anthraquinone (2) were synthesized by Wittig reaction. Their one-photon absorption and fluorescence, as well as two-photon absorption properties were investigated. These compounds showed strong intramolecular charge transfer bands as well as low fluorescence quantum yield. 1 showed a larger two-photon absorption cross-section of 1635 GM than that of 995 GM for 2 at the wavelength of 800 nm. Furthermore, the initiating properties of 1 and 2 were studied by two-photon induced polymerization. The resin with 1 as photoinitiator (R1) possessed higher sensitivity with a threshold energy 3.67 mW at the concentration of 0.02 wt% compared to that of 8.03 mW for 2. The resolution of polymer line, fabricated with R1 at the threshold with the linear scan speed of 50 μm/s, is 105 nm. This investigation on the relationship of resolution and sensitivity indicated higher sensitivity benefit to the improvement of microfabrication resolution.