A novel polymerization mechanism transformation strategy, involving anionic ring-opening polymerization and photoinduced cationic polymerization, is successfully applied for the synthesis of poly(ethylene oxide)-graft-poly(isobutyl vinyl ether) (PEO-g-PIBVE). First, poly(ethylene oxide-co-ethoxyl vinyl glycidyl ether) [P(EO-co-EVGE)] is synthesized by living anionic polymerization. The vinyl moieties of the functional PEO-based polymer are converted to the hydrogen iodide adduct by photolysis of diphenyliodonium iodide, monitored using NMR spectroscopy. A modified mode of Lewis acid-catalyzed living cationic polymerization is performed as a grafting from method to generate PIBVE segments grafted onto the PEO main chain. Both the intermediates and the final graft copolymers are characterized by gel-permeation chromatography (GPC) and H-1 NMR analysis.