N-acetyl-4-nitro-1-naphthylamine as sensitizer of N,N-dimethylaniline for photoinitiated radical polymerization

Photophysical, photochemical behaviour of N-acetyl-4-nitro-1-napthylamine ( ANNA) in the presence of N,N-dimethylaniline (DMA) was analyzed to establis h the influence of the nature of this nitroaromatic initiator on the photos ensitized generation of free radicals during photoinitiated polymerization of lauryl acrylate (LA) monomer. Steady-state (365 nm) photolysis was studi ed providing experimental evidence of a photosensitization process of DMA t hrough excitation energy transfer from ANNA. The dependence of the consumpt ion rate of both reactants on the irradiation time reveals that up to 87 mo lecules of DMA are consumed for each ANNA molecule photoreduced in spite of the low photoreduction quantum yield of ANNA induced by DMA. The efficienc y of the ANNA/DMA system as photoinitiator was studied by following the pol ymerization kinetics of LA monomer by Differential Scanning Photo-Calorimet ry (Photo-DSC). The photosensitization of DMA, working concurrently to the photoreduction reaction, induces a polymerization efficiency up to 5 times higher than that reached with other nitroaromatic initiators. (C) 2000 Else vier Science Ltd. All rights reserved.