The photocuring process of the diglycidyl ether of bisphenol A (DGEBA) with the bislactone 1,6-dioxaspiro[4,4]nonane-2,7-dione (s(gamma-BL)) was studied. Triaryl-sulfionium hexafluoroantimonate was employed as photoinitiator. FTIR/ATR was used to study the evolution of epoxy, lactone, and intermediate spiroorthoester groups to identify the different reactions that take place during the photocuring process. Photo-DSC and DSC were used to study the thermal evolution of the photocuring process and to assess the T-g of the fully cured material. Thermogravimetric analysis (TGA) was used to determine the thermal stability of the fully cured material. The thermo-mechanical properties of the materials were investigated using dynamic mechanical-thermal analysis. Shrinkage undergone during photocuring and gelation was studied with TMA. A strong influence of the photocuring temperature on the photocuring process of the DGEBA- s(gamma-BL) system was observed. Differences in the reactivity of the different species were observed with respect to the thermally cured system using ytterbium triflate as cationic thermal initiator. As a consequence, photocured materials exhibited a superior thermal stability and lower flexibility. (c) 2007 Wiley Periodicals, Inc.