Photopolymerization reactions initiated by a visible light photoinitiating system: Cyanine dye/borate salt/1,3,5‐triazine

Abstract

New three‐component photoinitiating systems consisting of a cyanine dye, borate salt, and a 1,3,5‐triazine derivative were investigated by measuring their photoinitiation activities and through fluorescence quenching experiments. Polymerization kinetic studies based on the microcalorimetric method revealed a significant increase in polymerization rate when the concentration of n‐butyltriphenylborate salt or the 1,3,5‐triazine derivative were increased. The photo‐induced electron transfer process between electron donor and electron acceptor was studied by means of fluorescence quenching and SrEt change of the fluorescence intensity. The experiments performed documented that an increase of the n‐butyltriphenylborate salt concentration dramatically increases the rate of dye fluorescence quenching, whereas the increasing of the 1,3,5‐triazine derivative concentration slows down the consumption of the dye. We conclude that the primary photochemical reaction involves an electron transfer from the n‐butyltriphenylborate anion to the excited singlet state of the dye, followed by the reaction of the 1,3,5‐triazine derivative with the resulting dye radical to regenerate the original dye. This reaction simultaneously produces a triazinyl radical anion derived from the 1,3,5‐triazine, which undergoes the carbon‐halogen bond cleavage yielding radicals active in initiation of a free radical polymerization chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3626–3636, 2007

Visible light sensitive photoinitiating systems: Recent progress in cationic and radical photopolymerization reactions under soft conditions

“…To the contrary, a real progress has been made in the synthesis of new chemical skeletons and new modifications of existing structures, as well as in the use of new additives: this has allowed the proposal of a large number of novel PIs and PISs. The mechanisms encountered in these systems are schematically depicted in reactions (1)-(7) [10][11][12][13][14][15][16]: after light absorption, PI interacts with one or two additives (e.g., iodonium salt, amine, N-vinylcarbazole, silane, chloro triazine, etc. ; Scheme 1) to generate initiating radicals for free radical polymerization (FRP; reactions (1)-(3a) and (6)) of (meth)acrylates or thiol-ene polymerization (TEP; reactions (1), (2) and (5)), cations or radical cations for cationic polymerization (CP; reactions (1) and (2)) or free radical promoted cationic polymerization (FRPCP) of epoxides (reactions 1-3) or vinyl ethers (reactions (1), (2) and (4)); the concomitant cationic/radical polymerization CCRP (hybrid cure) of a cationic monomer/radical monomer blend can also be achieved for the manufacture of interpenetrated polymer networks IPNs.…”

Triazine‐Based Type‐II Photoinitiating System for Free Radical Photopolymerization: Mechanism, Efficiency, and Modeling

“…Among the numerous PCIS redox additives reported in the literature, triazine derivatives (Tz) have been extensively used as electronacceptors in combination with amines, [12][13][14][15][16][17] thiols, [18] or borate salts. [18][19][20][21] They have been found to enhance final conversion and rate of polymerization by reacting with the semi-reduced form of the PI. Indeed, fundamental state of the PI is regenerated and can participate to a new cycle while the semi-reduced form of the triazine (Tz •− ) is expected to produce a triazinyl initiating radical (Tz -Cl • ) by dissociation of a CCl bond.…”

“…[12,13,19] Therefore, it was found quite interesting to evaluate the initiating efficiency of triazine S (TS) using ITX as versatile photoinitiator. [23] Figure 1a time is low and the maximum R p value is 0.82 m s −1 at 1.9 s (Figure 1b).…”

Photopolymerization as a promising method to sense biorecognition events

“…species were assumed to probably bind the growing chains terminating their expansion. The triazine derivatives would oxidize that radical species restoring the initial neutral initiator molecules, which could re-enter the photopolymerization process 187 , and a negative charged triazine compound that might generate new radicals involved in chain growth 186,188,189 . Figura.…”