Iterative synthesis of monodisperse PEG homostars and linear heterobifunctional PEG

Highly monodisperse, heterobifunctional poly(ethylene glycol) (PEG) was prepared by iterative chain extension of a PEGylated homostar using an octagol (EG8) building block to give MeO–EG24–OH in high purity. The branched structure facilitated purification of intermediates by chromatography, and mono-functionalization of the chain termini. This approach should be extendable to other classes of oligomers.