2-Methylol-thioxanthone (TX-M) was synthesized and characterized as a new photoinitiator. Photopolymerization experiments were performed with methyl methacrylate and also trimethylolpropanetriacrylate (TMPTA) as a multifunctional monomer in the presence of TX-M with N-methyl diethanol amine. Polymerization did not occur in an air atmosphere with TX-M without adding MDEA. The inhibiting effect of oxygen on the rate of polymerization was observed to be due to quenching of the triplet radicals by the carbonyl compound (TX-M). (c) 2007 Elsevier B.V. All rights reserved.