Photosensitization of carbazole derivatives in cationic polymerization with a novel sensitivity to near-UV light

Abstract

Photosensitizers based on the carbazole structure were designed and developed for cationic polymerization. Along with triarylsulfonium and diaryliodonium salts, the carbazole derivatives showed a high photosensitization effect in the cationic photopolymerization of epoxides. The photophysical properties of the carbazole derivatives were studied in terms of electronic absorption, fluorescence, and phosphorescence spectrometry. Moreover, a unique photosensitization mechanism of the carbazole derivatives was discussed after studies of the fluorescence quenching, redox behavior, and kinetics of the photopolymerization by time‐resolved fluorescence spectrometry, cyclic voltammetry, and photo differential scanning calorimetry, respectively. The results confirmed the redox photosensitization of the carbazole derivatives in cationic polymerization. The photosensitization of the carbazole and its ring or N‐alkylated derivatives occurred predominantly in singlet excited states at the rate of the diffusion limit, whereas the carbazole derivatives with carbonyl substituents sensitized onium salts via triplet excited states on the basis of the Rehm–Weller equation in the photoinduced electron‐transfer process. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 90–100, 2000

Phenothiazine Photosensitizers for Onium Salt Photoinitiated Cationic Polymerization

“…We have reported extensively on our studies in this area 2 ' 3,4 and other investigators have also been active in this field. 5,6,7,8 There are several mechanisms by which the photosensitization of onium salts take place, however, electron-transfer photosensitization appears to be the most efficient and generally applicable process. 9 A generalized mechanism for the electron-transfer photosensitization of diaryliodonium salts is shown in Scheme 1.…”

Poly(N‐vinylcarbazole)–clay nanocomposite materials prepared by photoinitiated polymerization with triarylsulfonium salt initiator

“…Figure 8 shows the UV–visible absorbance spectra of pure PNVC and PCN materials in THF solutions. There are two absorbance bands observed at around 250 and 330 nm that may be attributed to π–π* absorptions of the aromatic chromophores of the carbazole units in the polymer 25. The wavelengths of pure PNVC and PCN materials in the UV–visible regions are gradually affected by the presence of clay loading in the PCN materials as illustrated in Table I.…”

Monomeric and Polymeric Carbazole Photosensitizers for Photoinitiated Cationic Polymerization

“…[12] Previously, we have reported that a wide variety of electron-rich polynuclear aromatic compounds are efficient electron-transfer photosensitizers for all three onium salt cationic photoinitiators (I-III). [13] More recently, Chen et al [14] have described studies of the photosensitized photolysis of onium salts I and II by various compounds containing the carbazole nucleus. We have also reported that 9-vinylcarbazole (NVK), [15] its polymer (poly(9-vinylcarbazole)) and copolymers with other vinyl monomers [16] are excellent electron-transfer photosensitizers for onium salt photoinitiators.…”