Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

Abstract

SummaryThe combination of a dye which absorbs the photon, an electron acceptor and an electron donor leading to energy conversion through electron transfer, was the basis of the so called three-component systems. In this paper, an experimental work combining Rose bengal dye with a triazine derivative as electron acceptor and ethyl 4-(dimethylamino)benzoate as electron donor, will underline the benefit of the photocyclic behavior of three-component systems leading to the dye regeneration. A thermodynamic approach of the photocycle is presented, followed by a mechanistic and computational study of ideal photocycles, in order to outline the specific kinetics occuring in so called photocatalytic systems. The simple kinetic model used is enough to outline the benefit of the cyclic system and to give the basic requirements in term of chemical combination needed to be fulfilled in order to obtain a photocatalytic behavior.

Photochemical Study of a Three‐Component Photocyclic Initiating System for Free Radical Photopolymerization: Implementing a Model for Digital Light Processing 3D Printing

“…t crit values are always higher than t inhib values, meaning that the time to reach gelation is higher than the time to consume all dissolved oxygen. This is in contrast to a recent work and indicates that the critical time is the sum of the inhibition time plus the time needed to convert the monomer up to Conv crit . The time gap between t crit and t inhib is large at low irradiance (≈15 s) but decreases when the irradiance increases.…”

“…reached in the system is at best equal to dye concentration, whereas in three component PIS exhibiting photocyclic behaviour, [R . ] could be close to the co‐initiators concentration . The ratio in initiating radical concentration being 10 to 100 times between these two cases as a consequence of the dye recovery in photocyclic systems.…”

“…The ratio in initiating radical concentration being 10 to 100 times between these two cases as a consequence of the dye recovery in photocyclic systems. Additionally, photocyclic mechanism leads to the production of up to two initiating radicals per absorbed photon, one created by the oxidative species and another one formed from the reductive species . This shows the outstanding performance of photocyclic initiating systems over conventional two‐component photoinitiating ones.…”

High Performance Photoinitiating Systems: Application to Holographic Grating Recording

“…Photopolymerization process occurring during holographic grating recording is different from homogeneous photopolymerization as done previously: indeed, a three-dimensional image is built through the sinusoidal irradiation of the interference pattern [10][11][12]. This induces inhomogeneous photopolymerization of the photosensitive recording medium at the submicrometer scale, leading to refractive index modulations in the polymerized matrix (see Scheme 2).…”

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

“…Triplet-triplet annihilation was also taken into account, as its rate constant is quite high (k TTA = 7 ± 3 × 10 9 m −1 s −1 [57] ). Expressions of the rate constants of singlet (k dea1 ) and triplet (k dea3 ) deactivation (by either radiative or nonradiative pathways) as well as intersystem crossing rate constant (k ISC ) have been determined in a previous study (Equations (6)- (8)) [58] k…”