The rapid development of 3D printing using visible light as an irradiation source requires efficient visible light photoinitiators to realize a fast and reliable 3D printing process. Based on the photocleavage concept, a series of symmetric bifunctional photoinitiators comprising oxime‐ester moieties as latent initiation functionalities and conjugated carbazole as chromophores was synthesized. The impact of substitution position and the types of radicals on photophysical and photochemical behavior was investigated via experimental tests combined with quantum‐chemical calculations. The conjugated carbazole‐based oxime esters exhibit broad absorption bands from 250 to 400 nm and an interesting photobleaching property was observed during photolysis. Under 405 nm LED irradiation, the photoinitiation efficiency of the novel photoinitiators is comparable to that of the commercial visible light photoinitiator TPO. A vertical resolution of 50 μm was obtained when using oxime esters as photoinitiators in DLP 3D printing to fabricate delicate objects. The A‐π‐D‐π‐A core structures impart sufficient two‐photon cross sections (102–136 GM) to the oxime esters, enabling the construction of complex 3D microstructures of nanometer spatial resolution with two‐photon 3D printing technology. Notably, the threshold energy of the formulation containing 4d is lower than that of the commercial two‐photon resists IP−L. Also, the thermal stability of the PIs (>160 °C) is sufficient for daily storage.

A coumarinacyl anilinium (CAA) salt, facilely synthesized via a one-pot reaction, is shown to be a versatile visible and NIR photoinitiator for cationic and step-growth polymerizations. CAA salt exhibits superior photoinitiation performance as compared to commercial iodonium salt in cationic polymerization. Upon visible-light irradiation, this salt undergoes hemolytic and heterolytic cleavage and subsequent electron transfer and hydrogen abstraction reactions, forming reactive species capable of initiating cationic polymerization of epoxides and vinyl monomers. After a short irradiation period, polymerization also proceeds in the dark due to the non-nucleophilic nature of the counteranion. NIR-induced polymerizations were successfully conducted based on upconversion photochemistry. CAA salt can also initiate step-growth polymerization of N-ethyl carbazole (NEC) by oxidation of the monomer by the photochemically formed anilium radical cations. Subsequent proton release and radical coupling reactions essentially yield polycarbazole. CAA salt, featuring straightforward synthesis and long-wavelength sensitivity as well as versatile photoinitiating performance, has great potential in various applications.

In this work, photoinduced thiol-epoxy click reaction for side-chain functionalization, chain-extension, grafting, and cross-linking of polymers prepared by atom transfer radical polymerization by using 1,5-diazabicyclo[5.4.0]undec-5-ene thioxanthone acetate (Tx-DBU) as a photo base generator (PBG) is described. Irradiation of Tx-DBU at 365 nm leads to the generation of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in neutral form as a super base. DBU is capable of abstracting protons from thiols and thus formed thiolates are excellent nucleophiles that exhibit high affinity toward electrophiles such as epoxide rings. Appropriately selected thiols are successfully used for the desired reactions. The precursors and resulting polymers are characterized using 1 H-NMR, Fourier transform infrared, gel permeation chromatography, and differential scanning calorimetry measurements. This study shows that the use PBGs can further be extended to the synthesis of various complex macromolecular structures by the described post modification processes.

Chemiluminescence (CL) has recently emerged as a novel light source for triggering various photoreactions with appealing features such as the elimination of continuous power supply and complex instrumentation. Here, CL‐induced cationic photopolymerization using ferrocenium salts as unimolecular photoinitiators is reported. The ferrocenium salts, facilely synthesized via ligand exchange reactions, absorb the visible light emitted from CL reactions and generate Lewis acids capable of initiating the cationic polymerization of oxirane and vinyl monomers. The presented method can be applied to create linear polymer chains and cross‐linked luminescent polymer networks, which have significant potential in the fabrication of new polymeric materials and various bioapplications.