New BODIPY Dyes Based on Benzoxazole as Photosensitizers in Radical Polymerization of Acrylate Monomers

Abstract

A series of 2-phenacylbenzoxazole difluoroboranes named BODIPY dyes (1–8) was designed and applied as photosensitizers (PS) for radical photopolymerization of acrylate monomer. The light absorption within the ultraviolet-visible (UV–Vis) range (λmax = 350–410 nm; εmax = 23,000–42,500 M−1cm−1), that is strongly influenced by the substituents on the C3 and C4 atoms of phenyl ring, matched the emission of the Omnicure S2000 light within 320–500 nm. The photosensitizer possess fluorescence quantum yield from about 0.005 to 0.99. The 2-phenacylbenzoxazole difluoroboranes, together with borate salt (Bor), iodonium salt (Iod) or pyridinium salt (Pyr) acting as co-initiators, can generate active radicals upon the irradiation with a High Pressure Mercury Lamp which initiates a high-performance UV–Vis light-induced radical polymerization at 320–500 nm. The polymers obtained are characterized by strong photoluminescence. It was found that the type of radical generator (co-initiator) has a significant effect on the kinetic of radical polymerization of acrylate monomer. Moreover, the chemical structure of the BODIPY dyes does not influence the photoinitiating ability of the photoinitiator. The concentration of the photoinitiating system affects the photoinitiating performance. These 2-phenacylbenzoxazole difluoroborane-based photoinitiating systems have promising applications in UV–Vis-light induced polymerization.

Free-Radical Photopolymerization for Curing Products for Refinish Coatings Market

“…In addition, there are other bimolecular photoinitiators, not described here, which are among the most common components used in photoinitiating systems in the last decade, including, among others, polymethine dyes [ 52 , 109 ], squaric acid derivatives [ 110 , 111 , 112 ] or BODIPY dyes [ 112 , 113 ].…”

Recent Advances in Visible Light Photoinitiating Systems Based on Flavonoids

“…For decades, a great deal of effort has been devoted to developing greener photopolymerization processes, consisting in the use of biosourced photoinitiators and/or biosourced monomers [27][28][29], the use of sunlight instead of artificial light to initiate the polymerization [30][31][32][33][34][35] or the development of water-soluble photoinitiating systems enabling to avoid the use of organic solvents [36][37][38][39]. In order to identify the appropriate scaffold for designing high-performance visible light photoinitiators, a wide range of structures have been screened over the years, as exemplified with diketopyrrolopyrroles [40], bodipy [41][42][43][44][45][46], perylenes [47], dithienophosphole derivatives [48], thiophenes [49], cyclohexanones [50][51][52], quinoxalines [53][54][55][56][57][58][59][60][61][62][63][64][65][66], glyoxylates [67], cyanines [68], benzylidene ketones [69][70]…”