Photosensitization of N,N-Dimethylaniline by N,N-Dimethyl-4-nitroaniline as a New Bimolecular Photoinitiation System for Polymerization

Abstract

Photophisics, photochemical and polymerization activity of N,N-dimethyl-4-nitroaniline (DMNA) alone and in the presence of N,N-dimethyl-4 (DMNA) as coinitiator were analyzed to elucidate the influence of the bifunctional character of this compound on the efficiency and mechanism of generating inititing radicals. The presence of electron donor and acceptor groups in the same moleci=ule determines the capability of DMNA to initiate the polymerozation with higher efficiency and lower initiator consumption as compared with conventional bifunctional ketones. Detailed studies of the spectroscopy of both reactants were carried out providing experimental evidence of photosensitization of DMA throught excitation energy transfer from DMNA. The consumption rate of both reactants reveals that up to 165 molecules of DMA are consumed for each DMNA molecule phoreduced in spit of the low photoreduction quantum yield of DMNA induced by DMA. The photosensitization of DMA, working concurrently to the photoreduction reaction, enhances the polymerization efficiency as compared with other nitroaromatic initiators.