The discovery and development of onium salt cationic photoinitiators

Photoinitiated Polymerization: Advances, Challenges, and Opportunities

“…The photochemistry and applications of the direct initiation to cationic polymerization to a variety of epoxy and vinyl ethers have been well studied and subject to review articles 10,[138][139][140][141] and chapters in books. [1][2][3]42 In recent years, however, interest has been directed toward the development of strategies to make onium salt photoinitiators responsive to light with wavelengths in the near-UV and visible region of the spectrum.…”

A [(NHC)CuCl] complex as a latent Click catalyst

“…As a consequence of this inherent property of latency, such catalysts are widely utilized in industrial applications such as adhesives, paintings, coatings, inks 25 and photoresists. 3 The current scope of this chemistry is not reduced to polyadditions; hydrosilylation 4 and metathesis 5 reactions have also been studied. The concept of latent catalysis can be seen as switching on and off a chemical transformation.…”

Controlled Photoradical Polymerization Mediated by 2,2,6,6-Tetramethylpiperidine-1-Oxyl

“…Whereas no BAI fragments were inserted into the polymer structure prepared from AIBN/MTEMPO, the polymer obtained from CMTMP contained the BAI fragment in its structure, because the aromatic proton signals originating from BAI were discerned at 7.21-7.40 and 7.85-7.92 ppm. The formation of the phenyl radical is supported by the decomposition mechanism of the photo-acid generator [68][69][70]. The initiation by the phenyl radical was also confirmed by the experiment in which the uncontrolled photopolymerization of MMA performed in the presence of BAI without CMTMP produced a polymer with Mn = 62,800 and Mw/Mn = 3.77 at 84% conversion within only 2 h. During the MTEMPO-mediated polymerization, the propagating chains formed by the phenyl radical probably participated in the controlled polymerization by MTEMPO by obtaining the counter radical from the hydroxylamine (Scheme 4) because the GPC curves were shifted to the higher molecular weight side without deactivation with the increasing conversion.…”

“…In the MTEMPO/AIBN system, the propagation proceeded by repeating the dissociation and recombination of the C-ON bond, as well as the thermal polymerization, since no BAI fragments were contained in the polymer structure. However, electron transfer is expected to occur between MTEMPO and BAI in the excited state during the dissociation and recombination when it is taken into consideration that continued polymerization is difficult in the absence of BAI and that the excited diphenyliodonium salt easily receives an electron [68][69][70]. Consequently, the mechanism of the polymerization was thus proposed (Scheme 5).…”