Crystallization behavior and micelle formation of star-shaped amphiphilic block copolymer based on dendritic poly(ether-amide)

The star-shaped amphiphilic block copolymer (DPEA-PCL-PEG) was prepared through ring opening polymerization of E-caprolactone (CL) initiated by hydroxyl end-capped dendritic poly(ether-amide) (DPEA-OH), then coupling with monomethoxy-terminated poly(ethylene-glycol) (PEG) via an esterification process. The molecular structure was verified by FT-IR, H-1 NMR and gel permeation chromatography (GPC). The number average molecular weight of the PCL arm was calculated to be about 1910 g mol(-1) by H-1 NMR analysis. The number average molecular weight of the copolymer was determined to be 74,020 with the molecular weight distribution of 1.15 by GPC. The DSC and X-ray diffraction analysis indicated that the copolymer possesses double melting and crystallization peaks, attributed to PCL and PEG segments in DPEA-PCL-PEG. The corresponding melting and crystallization temperature, and value of crystallinity are much lower than that of their individual homopolymers. The copolymer easily formed the core-shell structural nanoparticles as micelles in water with a lower critical micelle concentration of 5.524 mg 1(-1). (c) 2007 Elsevier Ltd. All rights reserved.