Time-Resolved Spectroscopic and Density Functional Theory Study of the Photochemistry of Irgacure-2959 in an Aqueous Solution

Abstract

The photocleavage reaction mechanism of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure-2959) was investigated using femtosecond (fs) and nanosecond (ns) transient absorption (-TA) spectroscopy and also picosecond (ps) and nanosecond (ns) time-resolved resonance Raman (-TR(3)) spectroscopy experiments in a water-rich (volume ratio of acetonitrile/water = 3:7) solution. TA spectroscopy was used to study the dynamics of the benzoyl radical growth and decay as well as to investigate the radical quenching process by the radical scavenger methyl acrylate. ps- and ns-TR(3) spectroscopies were employed to monitor the formation of the benzoyl radical and also to characterize its electronic and structural properties. The fs-TA experiments results indicate that the Irgacure-2959 lowest lying excited singlet state S1 underwent efficient intersystem crossing (ISC) to convert into its triplet state with a time constant of 4 ps. Subsequently, this triplet species dissociated into the benzoyl and alkyl radicals with a corresponding maximum absorption band at 415 nm. The TR(3) results in conjunction with results from DFT calculations confirmed that Irgacure-2959 cleaved into the benzoyl and alkyl radicals at a fast rate on the tens of picosecond time scale.

Gelatin-Methacryloyl Hydrogels: Towards Biofabrication-Based Tissue Repair

“…Yet, most of the reported literature uses gelMA with the photoinitiator 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, which is better known under its trade name Irgacure ® 2959 from BASF (formerly Ciba Specialty Chemicals). This water-soluble initiator, which dissociates into a benzoyl and ketyl-free radical upon UV light irradiation through an ∝-cleavage reaction [29], has a relatively low cytotoxicity compared with other photoinitiators [30]. Interestingly, deviations from the gold standard of using gelMA with Irgacure 2959, except for the use of styrenated gelatin with camphorquinone (which showed low cell viability), are all recent and one-off demonstrations.…”

Dynamic photopolymerization produces complex microstructures on hydrogels in a moldless approach to generate a 3D intestinal tissue model

“…In our experimental set-up (Figure 1(b)), the height of the container is significant. Due to the absorbance of light intensity by the photoinitiator, which can be estimated from the Beer-Lambert law, Da will change along the vertical axis (distance to the ligth source), z, as: For masks of R = 50 µm, a value that matches the anatomic dimensions of small intestinal villi microstructures, PEGDA hydrogels (D0 = 1 x 10 -10 m 2 s -1 , [O2]0 = 1 mol m -3 ), [15] maximum light intensity (centered at  = 313 nm), I = 9.75•10 -4 mol m -2 s -1 , and 1% w/v of Irgacure 2959 solution as photoinitiator ( = 0.29, and  ( = 313 nm) = m mol -1 ) [31], Da significantly changes with z (Figure 1(c)). Because our set-up is open to oxygen due to the PDMS pools and polystyrene support, distinguishable growing pathways were expected for different z values.…”

Highly efficient water-soluble visible light photoinitiators

“…Currently, almost exclusively 2‐hydroxy‐1‐[4‐(2‐hydroxyethoxy)phenyl]2‐methyl‐1‐propanone (Irgacure 2959 ® , Fig. ) is used when water solubility is required since years of research have not yet lead to a breakthrough in establishing well suitable water‐borne PIs . The advantages of Irgacure 2959 ( I2959 ) are high reactivity because of a Norrish Type I cleavage process and good biocompatibility.…”