On the role of N-vinylpyrrolidone in the aqueous radical-initiated copolymerization with PEGDA mediated by eosin Y in the presence of O₂

Abstract

A ground-state complex between eosin and N-vinylpyrrolidone impacts the photo-initiated synthesis of PEG hydrogels.

Experimental validation of eosin-mediated photo-redox polymerization mechanism and implications for signal amplification applications

“…It is important to note that most of the calculated t 0.2 or "gelation time" is taken up by oxygen inhibition, when radical polymerization cannot occur due to the presence of oxygen in the reaction droplet. 18,27 For example, in modeling the case of 0.4 μM eosin Y (Fig. 3), it took 90 seconds for eosin radical trianion and TEOA radical cation reactions to deplete oxygen completely in at least one point of the volume, but it is 115 seconds before double bond conversion reaches 0.2.…”

“…TEOA radical cations either decay to TEOA radicals, which propagate the radical polymerization of monomers, or react with oxygen to form stable iminium cations and superoxide. 27 Eosin radical trianions can also react with oxygen to regenerate eosin dianion (Fig. 1A).…”

“…For polymerization to occur at ambient conditions, a small amount of free eosin Y is added to the monomer solution 15 such that oxygen is sufficiently scavenged by eosin radical trianion and TEOA radical cation species in solution. 27,28 However, oxygen also plays a uniquely promotional role by regenerating eosin via oxidation of eosin radical trianions, allowing the photointiation process to continue even with low concentrations of eosin photoinitiator.…”

“…VP is commonly employed in acrylate photopolymerization reactions to reduce oxygen inhibition and enhance the rate of radical polymerization and final conversion. 25,27,29,30 When used for signal amplification, eosin photoinitiators are coupled to nucleic acids 16,22 or proteins 16,20,21,23 that specifically recognize captured biomarkers. Local photoinitiator concentration will increase when biodetection events occur, and polymer forms when the local concentration exceeds the minimum initiator threshold where propagation reactions become competitive with inhibition reactions.…”

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

“…Since most photocatalysts (PCs) exhibit sufficient visible-light absorption, photocatalyzed polymerization can be conducted under low-energy visible light irradiation conditions using sunlight and light-emitting diodes (LEDs) as light sources [ 12 , 13 ], which are safer for humans than UV light. Visible light-absorbing PCs have been widely used for numerous light-driven photocatalyzed radical polymerization reactions, including photocatalyzed free radical polymerization [ 14 , 15 , 16 ], photoinduced electron/energy transfer–reversible addition-fragmentation chain transfer [ 17 , 18 , 19 , 20 ], and photoredox-mediated atom transfer radical polymerization (ATRP) [ 21 , 22 , 23 , 24 ], which can used for a wide range of applications, such as 3D/4D printing [ 25 , 26 , 27 , 28 ], biosystems [ 28 , 29 , 30 ], hydrogels [ 28 , 29 , 31 , 32 , 33 ], dental materials [ 34 , 35 , 36 ], and coatings [ 37 , 38 ].…”