D‐π‐a‐type oxime sulfonate photoacid generators for cationic polymerization under UV–visible LED irradiation

Abstract

Four D-p-A-type nonionic oxime sulfonate photoacid generators (PAGs) have been designed and synthesized for use in light-emitting diode (LED) excitable cationic photoinitiators, in which N,N-diphenylamino was used as electron donor with trifluoroacetophenone-based oxime sulfonates (trifluoromethanoesulfonate and p-toluenesulfonate) as electron acceptor and substituted fluorene and biphenyl groups as the p-conjugated systems. PAG-Ben-Tol (with biphenyl and p-toluenesulfonate) and PAG-Flu-Tol (with fluorene and p-toluenesulfonate) showed high quantum yields of photoacid generation (0.33-0.50) and very good thermal stability (over 250 8C). The absorbance spectra of these PAGs were consistent with the emission spectra of commercially gained UV-visible LED light sources.The potential of these PAGs for cationic photoinitiators was tested in two cationic monomer systems. These PAGs needed low light intensity and low concentration for photopolymerization with high conversions of monomer, for example, over 80%, gained at 3.0 mW cm 22 from 365 to 470 nm LEDs. The photochemical mechanisms of these PAGs are comprehensively investigated and discussed in detail.

Photochromic Polymers Based on Fluorophenyl Oxime Ester Photoinitiators as Photoswitchable Molecules

“…The N−O bond of E-FBOXEs is involved in these Frontier orbitals. This strong electrondelocalization effect exhibits intramolecular charge transfer properties,41 which may be beneficial to the cleavage of the N− O bond.3.2. Photochemistry of E-FBOXEs.…”

Spotting Trends in Organocatalyzed and Other Organomediated (De)polymerizations and Polymer Functionalizations

“…[66,[73][74][75] These PAGs release sulfonic acids upon light-induced homolytic dissociation of their NÀ O bonds followed by proton abstraction from the surrounding media. [74,76] Recently, a bis-substituted thiophene-based chromophore containing iminosulfonate was described as a non-ionic PAG capable of polymerizing epoxides and vinyl esters upon 365-475 nm light irradiation. Complete conversion was achieved within 1 min using 1 wt % of PAG for the polymerization of an epoxide formulation (Figure 2c).…”

Novel chalcone derivatives with large conjugation structures as photosensitizers for versatile photopolymerization

“…[1][2][3][4][5] Photopolymerization is widely applied in various fields, such as microelectronics, 6 UV-cured coatings, 7 3D microfabrication, [8][9][10] nanotechnology, 11,12 and biomedical applications. 13 Efficient photoinitiators (PIs) or photoinitiation systems (PISs) play an essential role in photopolymerization as they induce the rapid conversion of monomers into polymers by absorbing the appropriate wavelengths of light and generating reactive species, such as free radicals, 14 cations, 15,16 or anions. 17 Thus, the light-absorption property of PISs is important for the development of photopolymerization.…”