Synthesis of heterobifunctional polyethylene glycols: Polymerization from functional initiators

AbstractThe large-scale synthesis of heterobifunctional polyethylene glycols (PEGs) with tightly controlled molecular weights ranging from 2 to 20 kDa is described. PEGs were prepared by the ring-opening polymerization of ethylene oxide (EO) initiated from a protected amine (N-dibenzyl), and a protected alcohol (O-trityl) initiator. Additionally, EO polymerizations from initiators bearing azide and alkyne, both prototypical “click” chemistry functionalities, are outlined. This demonstrates the first successful use of an initiator bearing either an azide or strained cycloalkyne functionality in an ethylene oxide polymerization. The key to the methodology proved to be the selection of base. The use of potassium naphthalenide or potassium hydride in paraffin wax was highly dependent on the initiator used