This article reports on the IN photopolymerization of acrylates without photoinitiators. Initiation of the reaction was achieved by direct excitation of the acrylates during irradiation with short-wavelength UV light by use of the 222-nm emission of a KrCl* excimer lamp. The reactivity of various acrylates was studied by real-time Fourier transform infrared-attenuated total reflection spectroscopy. The rate and the extent of the reaction within the layer were strongly dependent on the depth of penetration of UV light, which was determined by the molar extinction coefficient of the acrylate. (C) 2004 Wiley Periodicals, Inc.