Iodonium‐ and sulfonium‐type onium salts with counter anions of different nucleophilicities, namely [Al(O‐t‐C(CF3)4)4]−, [(CF3SO2)2N]−, SCN−, CF3‐SO3−, PF6−, and 3,5‐bis(methoxycarbonyl)benzenesulfonate, were investigated in both NIR and UV‐LED sensitized photoinitiated polymerizations at 790 nm and 395 nm wavelength exposures, respectively. The reactivity of the neutral sensitizer Sens1, and the cationic sensitizer Sens2 were examined in combination with the onium salts. The reaction rate was compared with isopropylthioxanthone (Sens3) as sensitizer. The reactivity of the initiating system is proposed to be associated with the conductivity of the salts in acrylate monomers such as tri(propylene glycol) (TPGDA), trimethylol propane triacrylate (TMPTA), and 1,6‐hexane diol diacrylate (HDDA). Salts carrying the [Al(O‐t‐C(CF3)4)4]− anion require new consideration of previously introduced models because the reactivity of the salts does not directly correlate with their conductivities. Rhodamine B lactone quantitatively probed formation of acidic cations between considering the reaction between [(t‐C4H9‐Ph)2I]+[Al(O‐t‐C(CF3)4)4]− and photoexcited Sens2 comprising either BF4−, PF6− or [Al(O‐t‐C(CF3)4)4]−. No significant differences were observed in terms of the reactivity.

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A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved.

The synthesis of step-growth polymers by photoinduced methods is a challenging issue in synthetic chemistry. Here, we report a single component near UV responsive photopolymerization system for step-growth polymerization of N-methylpyrrole (MPyr) and N-methylindole (MIn) by using phenacyl bromide (PAB). The obtained high molecular weight conjugated polymers were characterized by spectral and chromatographic methods. Detailed laser flash photolysis and spectroscopic studies revealed that polymerization proceeds by successive photoinduced cleavage of PAB followed by electron transfer, proton release and coupling processes. After photolysis, chain growth continues also in daylight or dark by acidic oxidation. The structural features of the polymers were investigated. PAB single component photoinitiator enables an efficient, rapid, room temperature step-growth polymerization process of MPyr and MIn that can be applied to other conjugated monomers.