Micelle Formation and Drug Partitioning in Poly(L-lactide)/Poly(ethylene glycol) Diblock Copolymers with Fixed Soft Segments

• Main Authors: Chi-Hung Tsai, 蔡其宏
• Other Authors: 胡孝光
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/68676178047279090131

碩士 === 國立臺灣科技大學 === 高分子工程系 === 91 === Abstract（PartⅠ） Methoxy Poly(ethylene glycol)(MePEG)/Poly(L-lactide) (PLLA) copolymers with MePEG（5000g/mole）and various PLLA length（monomer number from 114 to 314）were synthesized, and the critical micelle concentrations（CMC’s） at 25 to 45℃ for various copolymers were determined with fluorescence spectroscopy and pyrene probe. It is found that CMC’s increase with PLLA block length and temperature. The standard free energy of micellization, standard enthalpy of micellization, and standard entropy of micellization（all are negative values）decrease with PLLA length. It shows that micellization influence by both entropy and enthalpy factors. Data analysis based on Leibler theory of micellization, the Flory-Huggins interaction parameters for micelle core and water increase PLLA length, leading to the lowing of CMC. These core-water interaction parameters were decomposed into the enthalpic and entropic contribution, with the more signification effect by entropic component. The numerical simulation also shows that the core-water interaction parameter decreases with the hydrophilic PEG length. Abstract（PartⅡ） Methoxy Poly(ethylene glycol)(MePEG)/Poly(L-lactide) (PLLA) diblock copolymers in aqueous solutions and their drug encapsulation was investigated. Copolymer micelles with various length of PLLA (monomer number from 63 to 314) and constant MePEG (=5000g/mole) were characterized with dynamic light scattering and intrinsic viscometry. It is found that the micelle radius is proportional to the 0.35th power of PLLA block length, which is between the prediction for two limiting cases (very large core and shell, respectively) by Halperin. The core diameter is proportional to the 0.67th power of PLLA block length, where the exponent is equal to the theoretical value for the case that the core is much larger than the shell. The weight of Vitamin K3 drug into copolymer micelles increases with the PLLA length. In addition, the partition coefficient from the water phase to micelle is proportional to the 0.73th power of PLLA length, indicating that the density of drug in micelle core increases with micelle core size.