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M. Tromayer, P. Gruber, A. Rosspeintner, A. Ajami, W. Husinsky, F. Plasser, L. Gonzalez, E. Vauthey, A. Ovsianikov, R. Liska:
"Wavelength-optimized Two-Photon Polymerization Using Initiators Based on Multipolar Aminostyryl-1,3,5-triazines";
Scientific Reports, 8 (2018), 1727301 - 1727311.

Two-photon induced polymerization (2PP) based 3D printing is a powerful microfabrication tool.
Specialized two-photon initiators (2PIs) are critical components of the employed photosensitive
polymerizable formulations. This work investigates the cooperative enhancement of two-photon
absorption cross sections (σ2PA) in a series of 1,3,5-triazine-derivatives bearing 1-3 aminostyryldonor
arms, creating dipolar, quadrupolar and octupolar push-pull systems. The multipolar 2PIs were
successfully prepared and characterized, σ2PA were determined using z-scan at 800 nm as well as
spectrally resolved two-photon excited fluorescence measurements, and the results were compared
to high-level ab initio computations. Modern tunable femtosecond lasers allow 2PP-processing at
optimum wavelengths tailored to the absorption behavior of the 2PI. 2PP structuring tests revealed
that while performance at 800 nm is similar, at their respective σ2PA-maxima the octupolar triazinederivative
outperforms a well-established ketone-based quadrupolar reference 2PI, with significantly
lower fabrication threshold at exceedingly high writing speeds up to 200 mm/s and a broader window
for ideal processing parameters.

http://dx.doi.org/10.1038/s41598-018-35301-x