3 research outputs found
Wavelength-optimized two-photon polymerization using initiators based on multipolar aminostyryl-1,3,5-triazines
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 aminostyryl-donor 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 triazine-derivative 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
A Straightforward Synthesis and Structure–Activity Relationship of Highly Efficient Initiators for Two-Photon Polymerization
The development of practical two-photon absorption photoinitiators
(TPA PIs) has been slow due to their complicated syntheses often reliant
on expensive catalysts. These shortcomings have been a critical obstruction
for further advances in the promising field of two-photon-induced
photopolymerization (TPIP) technology. This paper describes a series
of linear and cyclic benzylidene ketone-based two-photon initiators
containing double bonds and dialkylamino groups synthesized in one
step via classical aldol condensation reactions. Systematic investigations
of structure–activity relationships were conducted via quantum-chemical
calculations and experimental tests. These results showed that the
size of the central ring significantly affected the excited state
energetics and emission quantum yields as well as the two-photon initiation
efficiency. In the TPIP tests the 4-methylcyclohexanone-based initiator
displayed much broader ideal processing windows than its counterparts
with a central five-membered ring and previously described highly
active TPA PIs. Surprisingly, a writing speed as high as 80 mm/s was
obtained for the microfabrication of complex 3D structures employing
acrylate-based formulations. These highly active TPA PIs also exhibit
excellent thermal stability and remain inert to one-photon excitation.
Straightforward synthesis combined with high TPA initiation efficiency
makes these novel initiators promising candidates for commercialization
A Straightforward Synthesis and Structure–Activity Relationship of Highly Efficient Initiators for Two-Photon Polymerization
The development of practical two-photon absorption photoinitiators
(TPA PIs) has been slow due to their complicated syntheses often reliant
on expensive catalysts. These shortcomings have been a critical obstruction
for further advances in the promising field of two-photon-induced
photopolymerization (TPIP) technology. This paper describes a series
of linear and cyclic benzylidene ketone-based two-photon initiators
containing double bonds and dialkylamino groups synthesized in one
step via classical aldol condensation reactions. Systematic investigations
of structure–activity relationships were conducted via quantum-chemical
calculations and experimental tests. These results showed that the
size of the central ring significantly affected the excited state
energetics and emission quantum yields as well as the two-photon initiation
efficiency. In the TPIP tests the 4-methylcyclohexanone-based initiator
displayed much broader ideal processing windows than its counterparts
with a central five-membered ring and previously described highly
active TPA PIs. Surprisingly, a writing speed as high as 80 mm/s was
obtained for the microfabrication of complex 3D structures employing
acrylate-based formulations. These highly active TPA PIs also exhibit
excellent thermal stability and remain inert to one-photon excitation.
Straightforward synthesis combined with high TPA initiation efficiency
makes these novel initiators promising candidates for commercialization