Unsaturated oligo(ether-ester) was prepared by ring-opening polymerization of butylene oxide (BO) with glycidyl methacrylate (GMA) in the presence of cationic catalyst BF3•O(C2H5)2. The effects of mol ratio of the initial components, amount of catalyst, temperature, and reaction times on the copolymerization reaction were examined. Oligo(ether-ester) were achieved in highest yield of 82% after reaction times of 4 h at 0°C Synthesized copolymer was characterized using spectroscopic (1H NMR and IR) and chemical analysis methods. The thermal degradation and softing points of oligo(ether-ester)-styrene composites were studied. It is shown that crosslinking of the unsaturated oligo(ether-ester) with styrene takes place through the use of thermostable materials. © 2008 Wiley Periodicals, Inc.