For instance, Reid and Elisseeff reported the incorporation of hydrolytically degradable hemiacetals into low molecular weight PEO templates using Fenton oxidation. Meanwhile, Bielawski and Liu demonstrated the direct conversion of poly(ethylene glycol) (PEG) to poly[(ethylene glycol)-co-(glycolic acid)] via RuO4-mediated oxidation to form degradable ester groups. However, these methods had limitations in accommodating other functionalities.