Poly(ethylene oxide) (PEO)/poly(ethylene glycol) (PEG) is a synthetic polymer that is hydrophilic and has a wide range of applications in various fields, including energy harvesting devices, everyday consumables, and specialized medical treatments. Researchers have shown an interest in functionalized PEO that possesses both the desirable characteristics of PEO and functional molecules. For example, the attachment of biologically relevant molecules at the ends of PEG chains, known as PEGylation, has been used to impact medicines such as the recent COVID-19 vaccines. Connecting functional molecules to PEO presents a synthetic challenge (Scheme 1). While copolymerization of ethylene oxide and functional epoxide has been pursued to introduce functionality on PEO chains (Scheme 1A), the inherent steric and electronic difference between unsubstituted ethylene oxide (EO) and substituted epoxide makes efficient copolymerizations difficult. Furthermore, finding versatile polymerization conditions that accommodate various functional epoxides has been challenging. Consequently, end-group modification of terminal hydroxy groups (PEGylation, Scheme 1B) has been predominantly employed. However, the installation of multiple functionalities is restricted due to the limited number of hydroxyl groups per chain. Moreover, the modification site is limited to the chain's end. Scheme 1. General strategies for functionalized PEO synthesis.