Studies On Morphology Of Amphiphilic Copolymer Blends Based On PEG

The two kinds of amphiphilic polymer of Methoxy poly(ethylene glycol)-cholesterol (MePEG-chol) and Methoxy polyethylene glycol)-stearic acid (MePEG-st) were used to prepare polymer blends, novel biomimetic mixed micelles and drug-loaded mixed micells. In order to investigate the interaction between the polymers and drug, indomethacin (IMC) was chosen as a hydrophobic drug to be incorporated into the inner core of the mixed micelles.The morphology of polymer blends, mixed micelles and drug-loaded mixed micelles was characterized by differential scanning calorimetry (DSC), X-ray diffraction, transmission electron microscopy (TEM) and polarized light microscope (PLM) methods.In MePEG-chol the transition of liquid crystal (LC) to crystal was found and in MePEG-st only spheric crystal was observed. There were both LC and spheric crystal in MePEG-chol/MePEG-st blends, and the diameter of spheric crystal increased with the growth of the molar ratio of MePEG-st.From the observation of TEM, the mixed micelles exhibited core-shell structures which showed the average diameter about 10 nm and the structure was considered to be used for the delivery of hydrophobic drugs. The crystallization of the hydrophobic cores of the mixed micelles was proved by DSC, and the melting temperature increased when the molar ratio of MePEG-chol decreased. The micelle formed by MePEG-chol can not crystallize.The morphology of polymer blends, mixed micelles and drug-loaded mixed micelles was compared. The DSC curves showed that the temperature of crystallization of mixed micelles was the highest. IMC crystallized in the inner core of micelles which is different from the physical blends of IMC and polymers.