A straightforward synthesis and structure-activity relationship of highly efficient initiators for two-photon polymerization

Zhiquan Li, Niklas Pucher, Klaus Cicha, Jan Torgersen, Samuel C. Ligon, Aliasghar Ajami, Wolfgang Husinsky, Arnulf Rosspeintner, Eric Vauthey, Sergej Naumov, Tom Scherzer, Jürgen Stampfl, Robert Liska

Research output: Contribution to journalArticlepeer-review

158 Scopus citations

Abstract

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.

Original languageEnglish
Pages (from-to)352-361
Number of pages10
JournalMacromolecules
Volume46
Issue number2
DOIs
StatePublished - 22 Jan 2013
Externally publishedYes

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