Photoinitiated free radical polymerization of methyl methacrylate(MMA) inaqueous solution via hydrogen abstraction mechanism was described. For this purpose, thioxanthone (TX) chromophoric group was chemically incorporated into beta-cyclodextrin (beta-CD) by a simple esterification process. The resulting thioxanthone photoinitiator (TX-beta-CD) exhibited similar spectral characteristics and photoactivity to that of the parent TX molecule. Host guest complexes of MMA with TX-beta-CD in water, in the presence of N-methyldiethanol amine (NMDEA) as a hydrogen donor, facilitated photoinitiated free radical polymerization in aqueous medium. The postulated mechanism is based on the intermolecular reaction of photoexcited triplet TX moiety of TX-beta-CD with NMDEA. The resulting amino alkyl radicals initiate the polymerization. (c) 2007 Elsevier B.V. All rights reserved.