On the interaction mechanism of radical photoinitiators with monomers

Role of the Medium on the Reactivity of Cleavable Photoinitiators in Photopolymerization Reactions

“…The dissociation quantum yields are drastically affected by the fact that the bimolecular quenching rate constant of the triplet state by MMA are usually higher than those obtained for acrylates (Table ): for example, for f , k q = 3.25 × 10 6 M -1 s -1 for MMA and k q = 2.2 × 10 5 M -1 s -1 for MA. Similar trends have been already observed. ,, Attempts were made to calculate the corrected dissociation quantum yields, but the large error associated with each parameter required prevent any reliable calculation. This is mostly due to the high reactivity of the MMA with triplet states and to the assumption made on addition rate constants.…”

“…Such an effect has been reported for aromatic ketones/(meth)acrylates, [13][14][15]17 and it has been found that the quenching rate constant is dependent on the enthalpy of formation of the corresponding 1,4-diradical. 17 However, for short triplet states, the monomer quenching is not a competitive reaction to the R cleavage process. Therefore, φ diss can be expressed by…”

Polymerization Photoinitiators with Near-Resonance Enhanced Two-Photon Absorption Cross-Section: Towards High-Resolution Photoresists with Improved Sensitivity

“…No accessible oxidation or reduction potential could be recorded within the electrochemical window (see Figure S7), a priori discarding the possibility of a photoinduced ET with any of the PIs during the photoinitiation process, in contrast with other literature reports. 89 This was further confirmed by a Stern-Volmer experiment 90 where evolution of the luminescence intensity of V-Shape and Oct was monitored upon incremental addition of increasing monomer (DPPHA) concentration (see Figure S8). As no evolution was seen even at high monomer concentration, it can be concluded that no electron or energy transfer takes place between the singlet excited state of V-Shape or Oct and the monomer.…”

Polymerization Photoinitiators with Near-Resonance Enhanced Two-Photon Absorption Cross-Section: Toward High-Resolution Photoresist with Improved Sensitivity

“…No accessible oxidation or reduction potential could be recorded within the electrochemical window (see Figure S7), a priori discarding the possibility of a photoinduced ET with any of the PIs during the photoinitiation process, in contrast with the other literature reports. 89 This was further confirmed by a Stern−Volmer experiment 90 where evolution of the luminescence intensity of V-Shape and Oct was monitored upon incremental addition of increasing monomer (DPPHA) concentration (see Figure S8). As no evolution was seen even at high monomer concentration, it can be concluded that no electron or energy transfer takes place between the singlet excited state of V-Shape or Oct and the monomer.…”