This article studies the crosslinking reactions of some polyethers containing double bonds on the side chains. Thermal crosslinking takes place in all cases, but is overlapped by the degradation process. So, a catalyst has to be used to obtain the cured material and avoid degradation. The best initiator appears to be dicumyl peroxide and the maximum crosslinking degree is achieved only with 5% (w/w). Thermogravimetric analyses are used to test the quality of the cured materials. IR spectroscopy shows that crosslinking actually takes place by polymerizing pendent double bonds. Furthermore, activation energies for thermal and radical initiated crosslinking are determined by means of dynamic DSC studies.