Polymerization of vinyl monomers photoinitiated byp-nitroaniline: Photoinitiation mechanism

Abstract

The polymerization rate of methyl methacrylate photoinitiated by p‐nitroacetanilide in the presence of triethylamine was measured as a function of the amine concentration in different media. The polymerization is more efficient in nonpolar medium (benzene/monomer). ESR studies show the formation of a nitro and an amino free radical, which are formed by photoinduced proton transfer from the amine to the nitro group. The amine radical is the active species that adds to the monomer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2269–2273, 2000

Photoreduction of 4-substituted nitrobenzenes by amines

“…The presence of the a-aminoalkyl radical was previously showed in the photolysis of the 4-nitroaniline in the presence of TEA. 22 Although, in this case the protonated nitrobenzene radical also was observed.…”

“…The intermediate observed in the EPR experiments was the protonated nitrobenzene radical. 22 The strong electron-donor character of the amine 4-substituent could increase the rate of the proton transfer process. The formation of protonated nitrobenzene radical has been proposed in the photolysis of aromatic nitro compounds in the presence of TEA, however the mechanism depends on the solvent and the nature of the nitro compound.…”

“…In a previous work using EPR spectroscopy we directly observed the nitroaniline and the amine neutral radicals. 22 In the present work, we studied the photoreduction by triethylamine of several nitrobenzenes with electron-donor and electron-withdrawing substituents in the 4-position in acetonitrile. The aim of this work is to obtain information on the effect of the 4-substitution in the photoreduction mechanism of these compounds, and on their efficiency as photoinitiators of the methyl methacrylate polymerization.…”

Synthesis of luminescent polymers in the UV light region from dimethacrylate monomer using novel quinoline dyes

“…Furthermore, the Rp max [Figure (b)] was observed 30 s after blue light expose with a conversion of 6.88%, which is a lower conversion. Its slow polymerization kinetic may be explained by photoinitiator quantum yields (0.65%), a lower quantum yield produces a reduction in radical initiator that influences polymerization, another factor is the nitro group in dye structure, which is reduced to amino group by proton transfer leading to a reduction of polymerization velocity/efficiency . However, for the crosslinked polymers this result is considered very good …”

“…Its slow polymerization kinetic may be explained by photoinitiator quantum yields (0.65%), 31 a lower quantum yield produces a reduction in radical initiator that influences polymerization, another factor is the nitro group in dye structure, which is reduced to amino group by proton transfer leading to a reduction of polymerization velocity/efficiency. 8,[31][32][33] However, for the crosslinked polymers this result is considered very good. 8,10 The Q-2 system had the highest conversion velocity.…”