Synthesis and characterization of dendritic star poly(L-lactide)s

Dendritic star poly(L-lactide)s (PLLAs) were prepared by ring opening polymerization using a hyperbranched aliphatic polyester as the core. The stars were characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR). The result shows the star PLLAs have narrow molecular weight distribution and the length of arms can be well controlled in terms of the molar ratios of L-lactide to the initiator. The structure and thermal properties of the star polymers were investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). XRD shows that the formation of star structure does not alter the structure of crystal of PLLA. The results of DSC indicate that the glass transition temperature (T-g) and the crystallinity of the star polymers increased with increasing the lengths of arms. It is identified that the crystallization of PLLA was effectively suppressed by the formation of star topology.