Conjugated Carbazole‐Based Schiff Bases as Photoinitiators: From Facile Synthesis to Efficient Two‐Photon Polymerization

Exploration of simple and economical synthetic routes to construct active two‐photon initiators (2PIs) with long conjugation length is highly desirable to promote the development of two‐photon‐induced photopolymerization technology. In this article, several conjugated carbazole‐based derivatives containing N=C bonds as π bridges and electron donor/acceptor groups were prepared through one‐step Schiff base reaction. The structure–activity relationship was systematically investigated through calculations and experimental tests. The results showed that compared to the D‐π‐D‐π‐D molecules, the A‐π‐D‐π‐A molecules exhibited stronger charge transfer, which induce redshifted linear absorption and enhanced two‐photon absorption at 800 nm. The 2PIs displayed aggregation‐induced emission property and show potential for the fabrication of luminescent microdevices. In two‐photon‐induced microfabrication tests, the formulations containing novel 2PIs exhibited lower threshold energy than the widely used commercial photoinitiator Irgacure 369 and the two‐photon resists IP‐L is the brand name of the two‐photon resist from Nanoscribe, specially designed for nanoscribe's laser lithography systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2692–2700