Penta‐Hydroxy Flavones‐Based Photoinitiating Systems for Free Radical, Cationic, and Thiol‐Ene Polymerization upon Exposure to Mild Blue LEDs

Abstract

Natural flavone-derivatives (i.e., morin and quercetin) are investigated as visible light-sensitive photoinitiators. The photochemical mechanisms of the radical generation from flavone-derivative-based photoinitiating systems (PISs) upon exposure to mild blue light-emitting diodes are studied. The impact of substituent site of functional groups on the photoinitiation ability is determined. The quercetin-based PISs exhibit more reactivity than the morin-based systems on free radical photopolymerization. Moreover, the investigated flavone-based PISs present their stabilities at room temperature, indicating that resin containing these systems barely require special storage requirements. Thiol-ene polymerization initiated by the flavone-derivatives-based PISs is also investigated.

Bio-sourced monomers and cationic photopolymerization–The green combination towards eco-friendly and non-toxic materials

“…Over the years, several natural compounds have been identified as interesting and efficient scaffolds for radical, cationic and thiol-ene photopolymerization reactions, such as anthraquinones [235,[256][257][258][259], carotenoids [230,231], various derivatives of chlorophyll [260,261], curcuminoids [18,250,251,[262][263][264][265][266], flavonoids [267][268][269][270][271][272][273], naphthoquinones [274,275], riboflavin [276][277][278][279][280][281] and lignin derivatives [282].…”

“…Final coatings evidenced excellent adherence properties as well as high thermal stability, thus promising successful applications of flavonols as efficient photosensitizers for the synthesis of antibacterial coatings for biomedical purposes. [267,270,273].…”

“…More recently, quercetin along with morin, another naturally occurring penta-hydroxy flavone (PHF, chemical structures are shown in Fig. 55), was further investigated as visible light-sensitive PI for the cationic polymerization of DVE-3 [273]. Steady state photolysis analyses confirmed a strong interaction between the PHFs and Iod when irradiated with a LED centred at 394 nm while photopolymerization experiments of DVE-3 carried out upon exposure to a LED bulb centred at 410 nm reached 89% and 78% of conversions for the quercetin/Iod and the morin/Iod PISs respectively.…”

“…. Chemical structures of the different flavonoids tested for the design of biosourced photoinitiating systems for cationic photopolymerization reactions[267,270,273].…”

Recent Advances in Visible Light Photoinitiating Systems Based on Flavonoids

“…The insensitivity of Gram-negative bacteria to singlet oxygen was assigned to the presence of lipopolysaccharides in the cell wall offering some protection against exogenous agents. More recently, quercitin and morin, which are two isomers of position, were compared for their photoinitiating abilities during the FRP of a BisGMA/TEGDMA (1/1) blend (where BisGMA and TEGDMA stand for bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate, respectively) or TMPTA, the cationic polymerization of tri(ethylene glycol) divinyl ether (DVE-3), and the polymerization thiol-ene of a DVE-3/trimethylolpropane tris(3-mercaptopropionate) (Trithiol) (1/1) blend or a 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (Trione)/Trithiol (1/1) blend (see Figure 8) [246]. Morin is a natural compound that can be extracted from Osage orange and is well known to exert antioxidant, anti-inflammatory and anti-carcinogenic effects [247][248][249][250].…”