Visible-Light Emulsion Photopolymerization of Acrylates and Methacrylates: Mechanistic Insights and Introduction of a Simplified Sulfur-Based Photoinitiating System

Abstract

photopolymerization with a much weaker initiating system. The method can also lead to the production of random copolymer latexes, such as P(MMA-co-St) as well as the film-forming P(MMA-co-BA). That the disulfide is able to lead to the former further supports the predominant role of the propagation rate on the polymerization. Finally, the polymerization allows for temporal control. It proceeds under light, and stops in the dark.

Visible‐Light Initiated Dispersion Photopolymerization of Styrene

“…In our previous studies, [17–18] we showed that the thiyl radicals generated from the homolytic cleavage of the S−S bond under visible light led to efficient emulsion polymerization of MMA, but not styrene. The combination of a greater MMA solubility in water and a k p value higher than for styrene was put forward to explain the observations.…”

“…It should be noted that the particle size did however not exceed 345 nm, i.e., a size similar to the maximum one observed in photoemulsion polymerizations. [17][18] The decrease of PEGMA concentration had a negative impact on the particle size distributions, with for example D w /D n = 1.09 at 18 wt % of PEGMA while at 5 wt % of PEGMA, D w /D n = 1.25 (Figure S4). As mentioned above, the obtention of broad PSDs for all samples may be due to the rather slow generation of radicals from our PIS resulting in a low and continuous nucleation, as shown by the evolution of particle number (N p ) with conversion (Figure S5).…”

“…[8][9][10][11][12][13][14][15][16] We showed that a Nheterocyclic carbene (NHC) borane-based PIS led to very stable latexes of polystyrene (PS) or poly(meth)acrylates by aqueous emulsion polymerization with solids contents up to 30 %. [17][18] The key step is the formation of an initiating boryl radical via hydrogen atom abstraction from a NHCborane co-initiator by a photogenerated thiyl radical. The diameter of the particles obtained ranged from 50 to 300 nm (Figure 1B, right).…”

Effect of surfactant concentration and monomer polarity on particle nucleation in emulsion step polymerization of dithiol with diene

“…With a few exceptions, this trend is generally observed in a radical chain polymerization and provides important guidance for formulators since most emulsion processes are performed in the range CMC < [S] < 4  CMC. For a typical anionic surfactant such as sodium dodecyl sulfate (SDS), the concentration used in emulsion polymerization is usually in the range 6-24 mM [20][21][22][23].…”

Mild Photocatalytic Synthesis of Azimines

“…As part of our exploration of light-driven reactions [29][30][31][32][33] we considered photocatalysis. UV photons were used to form nitrenes en route to the azimines.…”