A novel thermally degradable photocrosslinking system was investigated. Difunctional and trifunctional epoxides with tertiary ester linkages were synthesized. When blended films of epoxides and poly(vinyl phenol) or epoxides and poly(methacrylic acid-co-ethyl methacrylate) with a photoacid generator were irradiated and then baked at relatively low temperatures (<100 degreesC), the films became insoluble in solvents. The heating conditions strongly affected the insoluble fractions of the blends. The insoluble fractions of the blended films containing the trifunctional epoxide were higher than the fractions of the films containing the difunctional epoxide. The crosslinked films became soluble after baking at relatively high temperatures (>120 degreesC). The reaction pathway of the blended system was studied with in situ Fourier transform infrared measurements. (C) 2004 Wiley Periodicals, Inc.