Synthesis and properties of Pluronic-based pentablock copolymers with pendant amino groups

Amphiphilic Pluronic-based pentablock copolymers with pendant amino groups have been successfully synthesized via ring opening polymerization of gamma-(carbamic acid benzyl ester)-epsilon-caprolactone (gamma CAB epsilon CL) and epsilon-caprolactone (epsilon CL) using Pluronic F127 as macroinitiator and Sn(Oct)(2) as catalyst, and followed by hydrolysis of the Cbz protected groups under acidic conditions. The structure of the copolymer was confirmed by proton nuclear magnetic resonance (H-1 NMR) and Fourier transform infrared spectroscopy spectra. In addition, gel permeation chromatography results demonstrated that the synthetic copolymer had a single and symmetrical peak. Moreover, the crystallinity and hydrophilicity could be well adjusted by the content of the functionalized monomer. Successful formation of aggregates was demonstrated by fluorescence method and transmission electron microscopy revealed that the micelles had a spherical morphology and the size was on nano scale according to the laser particle sizer results. The polymeric micelles had no obvious cytotoxicity even the micelles concentration reached 500 mg/L. Thus the Pluronic-b-poly(gamma-amino-epsilon-caprolactone-co-epsilon-caprolactone) copolymers have great potential for the use in the biomedical fields.