A Straightforward Synthesis and Structure–Activity Relationship of Highly Efficient Initiators for Two-Photon Polymerization

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 an...