The cationic crosslinking of a polyacrylate bearing a spiroorthoester pendant group with mixtures of diglycidyl ether of bisphenol A and three phosphorus-containing glycidyl derivatives was carried out with ytterbium triflate as an initiator. The curing process was monitored with Fourier transform infrared spectroscopy. The thermomechanical and thermogravimetric properties were evaluated. The glass transition temperatures of the obtained materials were, in general, above 100 degrees C. The incorporation of phosphorus into the network increased the limiting oxygen index values, thus improving the flame retardancy of the materials. During crosslinking, all the crosslinked polymers showed slight shrinkage that was much lower than that observed in conventional epoxy resins. (c) 2006 Wiley Periodicals, Inc.