Novel A-π-D-π-A structure two-photon polymerization initiators based on phenothiazine and carbazole derivatives

Two-photon polymerization additive manufacturing has great demand for new and efficient two-photon initiators. Acetylene bridged A-pi-D-pi-A initiator molecules based on phenothiazine and carbazole were designed and synthesized via Sonogashira coupling reaction utilizing benzophenone and fluorenone as electron-donating groups. The ultraviolet-visible absorption spectra, fluorescence emission spectra, two-photon absorption cross section, two-photon fluorescence properties, as well as their photoinitiation properties as initiators, were studied. The results showed that different electron donors and acceptors directly affect the photophysical properties of molecules, and their effects are interrelated. Among them, under the action of femtosecond laser, the two-photon absorption cross section of the molecule with phenothiazine as the donor and benzophenone as the acceptor can reach 327 GM at 780 nm. Two-photon polymerization experiments have also proved that it can indeed initiate trimethylolpropane triacrylate photopolymerization for micro-/nano-manufacturing. The scanning rate reached 2000 mu m s(-1) at a laser power of 30 mW during the polymerization process, and the complete and clear three-dimensional structures were obtained. The highest resolution of the complete three-dimensional structure was about 280 nm.

Automated summary

The designed and synthesized two-photon initiator molecules exhibit excellent two-photon absorption and photoinitiation properties. Different electron donors and acceptors directly affect the photophysical properties of molecules, and their effects are interrelated.