Dimethyl Dihydroacridines as Photocatalysts in Organocatalyzed Atom Transfer Radical Polymerization of Acrylate Monomers

Abstract

Development of photocatalysts (PCs) with diverse properties has been essential in the advancement of organocatalyzeda tom transfer radical polymerization (O-ATRP). Dimethyl dihydroacridines are presented here as anew family of organic PCs,for the first time enabling controlled polymerization of challenging acrylate monomers by O-ATRP.S tructure-property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties,and accessing astrongly oxidizing 2 PCC + intermediate for efficient deactivation. In O-ATRP,t he combination of PC,i mplementation of continuous-flowr eactors,a nd promotion of deactivation through addition of LiBr are critical to producing well-defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen-tolerance of the system and application to diverse acrylate monomers,i ncluding the synthesis of well-defined di-and triblockcopolymers. Figure 1. a) Proposed mechanism of O-ATRP. b) Previously reported PCs developed for O-ATRP (left) with the new dimethyl-dihydroacridine PC family investigatedi nthis work (right).

Visible-Light-Curable Solvent-Free Acrylic Pressure-Sensitive Adhesives via Photoredox-Mediated Radical Polymerization

“…Three α-haloesters with suitable ground-state reduction potentials (E red ) were selected, and it was expected that the electron transfer would be favorable, considering that the excited-state oxidation potential (E ox *) of 4DP-IPN was -1.28 V vs. the saturated calomel electrode (SCE, Scheme 2). As presented in Scheme 2, the quantum chemical calculation and reported experimental data also supported our arguments [40,41]. The calculated ground-state reduction potentials (E red,cal ) of the selected α-haloesters were much less negative than the E ox * of 4DP-IPN, which are also well in accordance with the experimental reduction potentials (E red ).…”

“…Chemical structures of the 2,4,5,6-tetrakis (diphenylamino)-1,3-benzenedicarbonitrile (4DP-IPN) photocatalyst and α-haloesters (diethyl 2-bromo-2-methylmalonate (DBM), ethyl 2-bromopropionate (EBP), and ethyl α-bromoisobutyrate (EBiB); the experimental/computational redox potentials are also indicated. † Value was derived from reference [40]. ‡ Value was derived from reference [41].…”

A Practice‐Oriented Benchmark Strategy to Predict the UV‐Vis Spectra of Organic Photocatalysts**

“…In this work, we benchmark several exchange‐correlation functionals against handpicked reference data that consists of experimental spectra extracted then digitized from recent literature [15–25] . The main novelties in our strategy are: i) a spectral fitting procedure that takes into account full spectral shapes, not only individual excitations; ii) the excitation energies are scaled instead of shifted during the fitting to yield proportional changes throughout the fitted range; iii) the benchmark focuses on organic photocatalysts (OPCs).…”

Visible-Light Amine Thioxanthone Derivatives as Photoredox Catalysts for Photopolymerization Processes

“…It is possible by using strongly reducing organic photocatalysts, which are able to directly reduce activated alkyl bromide. 27 A broad group of organic compounds, e.g., perylene, 28,29 phenothiazine and its derivatives, 25,30 diaryl dihydrophenazine, 26,31 thienothiophene derivatives, 32 phenoxazine, 33 carbazole derivatives, 34 and 1,1′-bisnaphthol 35 were reported for the role of photocatalysts for photopolymerization of a methyl methacrylate monomer. These compounds enable atom transfer radical polymerization under UV irradiation or visible light.…”

“…The use of a metal-free variant of ATRP eliminates metal contamination in the polymer product that is undesirable for certain, for example, biomedical- and electronics-related applications. , Therefore, photoredox catalysis found application in photoinduced synthesis of polymer materials, performed in a control manner. It is possible by using strongly reducing organic photocatalysts, which are able to directly reduce activated alkyl bromide …”