Effect of the electron donor structure on the shelf‐lifetime of visible‐light activated three‐component initiator systems

Abstract

In this study, we investigated the effect of electron donor structures on the shelf life of three-component initiator systems which also included methylene blue (MB) as a photosensitizer and diphenyl iodonium salt (DPI) as an electron acceptor. For this research, N-phenylglycine (NPG), N-methyldiethanolamine (MDEA), N,N-diisopropyl-3-pentylamine (DIPA), and 1,4-diazabicyclo[2.2.2]octane (DABCO) were used as electron donors, with different of proton transfer efficiencies and radical/cation persistence. To aid characterization of the shelf-life or dark storage stability of threecomponent initiator systems, the relative polymerization kinetic profile of each freshly prepared initiator system was first obtained using photo-DSC. The standardized photopolymerization reactions were repeated after various dark storage intervals. Thermal stability of each initiator system was compared by applying a ramped temperature program to monomer samples in the DSC in the dark. To analyze the kinetic changes as a function of storage time more quantitatively, we suggested an equation and characterized the shelflifetime constant (k) of three-component initiator systems.From the experiments and analysis, we conclude that the order of shelf-life is consistent with the of radical cation (DHÁ þ ) persistence; DABCO > DIPA > MDEA > NPG, and inversely related to the proton transfer efficiency of the electron donor; NPG > MDEA > DIPA > DABCO. The effects of electron donor structures on thermal stability were consistent with the results of kinetic shelf-life experiments. This investigation provides an effective means to characterize as well as predict shelf lifetimes of initiator systems.

Structural Effects in the Iridium Complex Series: Photoredox Catalysis and Photoinitiation of Polymerization Reactions under Visible Lights

“…For all complexes, the Ir /Iod interaction reactions are highly favorable according to the highly negative free energy change (Table ; e.g., Δ G = −1.28 and −1.41 eV for Ir_3 and Ir_12 , respectively; using E red (Ph 2 I + ) = −0.2 V) . The same holds true for the Ir /MDEA reactions (e.g., Δ G = −0.89 eV for Ir_12 ; using E ox (MDEA) = 1 V) …”

Photo-curing kinetics of hydroxyethyl acrylate (HEA): synergetic effect of dye/amine photoinitiator systems

“…The photoinitiation mechanism in the presence of MB/ TEOA or AO/TEOA involves the electron transfer, followed by a proton transfer from the tertiary amine to the dye leading to the formation of amine radical (TEOA. ), which will initiate the polymerization, and the dye radical which acts as a terminating agent [12,30]. Figure 7b shows that the monomer conversion is about 90% in the first 35 s of irradiation, when AO photosensitizer is used, whereas is about 40% in the case of MB.…”

“…9. After irradiation, the excited dye reacts with amine to form the amine radical cation, this reaction is followed by proton transfer from the amine to the dye, leading to the formation of free radical active center capable to initiate polymerization, and the dye radicals act as terminating agents, according to the reaction below: It has been reported that the efficiency of amine as coinitiator depends on the radical cation persistence and the proton transfer ability [30,33]. More the proton transfer is delayed more the radical cation is persistent.…”

Patient‐reported outcome measures suitable to assessment of patient navigation

“…The three‐component systems showed an approximately fivefold increase in the polymerization rate. Three‐component photoinitiator systems including a light‐absorbing photosensitizer, an electron donor, and an electron acceptor for visible light‐activated free‐radical polymerization were also intensively investigated by Stansbury and coworkers 198–202. They used xanthene dyes (e.g., rose bengal and fluorescein), a phenazine dye (methylene blue), a porphin dye (5,10,15,20‐tetraphenyl‐21H,23H‐porphin zinc; Scheme ), or CQ as photosensitizer, various amines as electron donors, and a diphenyliodonium salt as electron acceptor.…”