The crosslinking of poly(ethylene oxide) (PEO) with a difunctional peroxide such as 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (Luperox 101) may proceed through at least two different pathways. Thus, the thermally formed alkoxy radicals abstract hydrogen from PEO, and the resulting PEO radicals may combine or react with the peroxide. radicals to give ether or acetal crosslinks. However, these reactions also produce noncrosslinking acetals and vinyl ethers. The acetals may react further with peroxy or other radicals and yield orthoesters and ketene acetals. These and similar groups, in the presence of dilute acids, are susceptible to acid hydrolysis, leading to the disintegration of the gels. The gels, upon swelling in dilute acids, undergo a slow degradation process that is not observed for unmodified PEO. The acid hydrolysis is confirmed by a combination of size exclusion chromatography and dynamic mechanical analysis. IR analysis shows the presence of hydroxyl end groups and the presence of carboxylates rather than aldehyde groups, this is consistent with orthoesters and ketene acetal intermediates.