A new chemical modification of saturated polymers involving free radical addition to mono-substituted alkynes is presented and examined in terms of reaction yield, graft structure, and changes to molecular weight. Solvent-free, peroxide-initiated reactions of ethyl propiolate and poly(ethylene oxide) provide good yields of ethyl (2-E,Z)-3-alkylacrylates, whereas less efficient hydrogen atom donation by polyethylene impacts negatively on reaction yields and encourages alkyne oligomerization. Model compounds are used to characterize alkyne grafting products, and to probe the relationship between reagent properties, reaction yields, and product structures. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7386-7394, 2008