Two kinds of end-functionalized poly(ε-caprolactone)s

maleimido-PCL and HS-PCL

were synthesized by the ring-opening polymerization of ε-caprolactone (ε-CL) with N-hydroxyl ethyl maleimide (HEME) and 2-mercaptoethanol (ME) as initiators

respectively.Polymerizations were catalyzed by tin (Ⅱ) trifluoromethane (Sn(OTf)2) in bulk under mild conditions.These polymers showed low polydispersities and have functional groups at both ends.Two glutathione-terminated poly(ε-caprolactone) (GS-PCL and GSS-PCL) were then synthesized by Michael addition reaction of the maleimido-PCL with glutathione

or the coupling reaction of HS-PCL with glutathione

respectively.The structures of the two amphiphilic polyesters were confirmed by 1H-NMR and GPC measurements.Glutathione groups on the chain end increased the hydrophilicity of PCL

therefore

the polyesters can self-assemble in aqueous buffer solutions.Transmission electron microscopy (TEM) measurements confirmed the formation of spherical aggregates with the diameter range from 20～80 nm

and the size of the aggregates was found to increase with the decease of the pH of the buffer.In addition

aggregates from GSS-PCL showed redox-sensitive properties.