Synthesis of a novel structural triblock copolymer of poly( γ -benzyl- l-glutamic acid)- b-poly(ethylene oxide)- b-poly( ε-caprolactone)

Abstract

A novel structural triblock copolymer of poly( γ-benzyl- l-glutamic acid)- b-poly(ethylene oxide)- b-poly( ε-caprolactone) (PBLG-PEO-PCL) was synthesized by a new approach in the following three steps: (1) sequential anionic ring opening polymerization (ROP) of ethylene oxide and ε-caprolactone with an acetonitrile/potassium naphthalene initiator system to obtain a diblock copolymer CN-PEO-PCL with a cyano end-group; (2) conversion of the CN end-group into NH 2 end-group by hydrogenation to obtain NH 2-PEO-PCL; (3) ROP of γ-benzyl- l-glutamate- N-carboxyanhydrides (Bz- l-GluNCA) with NH 2-PEO-PCL as macroinitiator to obtain the target triblock copolymer. The structures from CN-PEO precursor to the triblock copolymers were confirmed by FT-IR and 1H NMR spectroscopy, and their molecular weights were measured by gel permeation chromatography. The monomer of Bz- l-GluNCA can react almost quantitatively with the amino end-groups of NH 2-PEO-PCL macroinitiator by ROP.