Efficient synthesis of high purity homo-arm and mikto-arm poly(ethylene glycol) stars using epoxide and azide-alkyne coupling chemistry

High purity homo-arm and mikto-arm poly(ethylene glycol) (PEG) stars are successfully prepared by the combination of epoxide ring-openings and azide-alkyne click reactions. First, monohydroxy-PEG was modified via epoxide chemistry to bear one hydroxyl and one azide functionality at the same end. An alkyne-functionalized PEG chain was then coupled to the azide. Subsequently, the remaining hydroxyl could be reactivated to an azide again and again to enable stepwise addition of alkyne-functionalized polymer arms. The use of efficient reactions for this iterative route provides star polymers with an exact number of arms, and a tailorable degree of polymerization for each arm. Detailed characterization confirms the high purity of multi-arm polyethylene glycol products.