Co-assembly of Polyether - Poly(L-lactic acid) Diblock Copolymers and Iron(II,III) Oxide in Aqueous Solutions.

• Main Authors: Jun-Xian Zeng, 曾駿憲
• Other Authors: Shiaw-Guang Hu
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/ma8tc7

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 106 === This work is to synthesize methoxypoly(ethylene glycol)-poly(L-lactide) (mPEG-PLLA) diclock copolymers with three different lengths of hydrophobic (PLLA) segments by using ring-opening polymerization, and we used gel permeation chromatography (GPC) to determine the molecular weight of mPEG-PLLA diblock copolymer. mPEG-PLLA diblock copolymers and iron (Ⅱ, Ⅲ) oxide nanoparticles with 15-20 nm average particle size are co-assembled in deionized water by using co-precipitation method. Then we determined the critical micelle concentration (CMC) of diblock copolymers solution by using fluorescent probe with various concentrations of iron oxide nanoparticles and various degrees of polymerization (DP) of hydrophobic (PLLA) segments. And we discussed (1) the power-law exponents (a0) for the CMC versus the DP of hydrophobic segments of diblock copolymers at different concentrations of iron oxide nanoparticles, and (2) The power-law exponents (n0) for natural logarithm of CMC versus the concentrations of iron oxide nanoparticles at different DP of hydrophobic segments. Then we measured the average particle size of mPEG-PLLA diblock copolymer micelles in aqueous solutions by using dynamic light scattering (DLS) with various concentrations of iron oxide nanoparticles and various DP of hydrophobic segments. And we discussed (1) the power-law exponents (a) for the average particle size of micelle versus the DP of hydrophobic segments at different concentrations of iron (Ⅱ, Ⅲ) oxide nanoparticles. (2) The power-law exponents (n) for the average particle size of micelles versus the concentrations of iron oxide nanoparticles at different DP of hydrophobic segments. Last we measured the content of iron oxide nanoparticles in diblock copolymer micelles with various concentrations of iron oxide nanoparticles and various DP of hydrophobic segments by using thermogravimetric analysis (TGA). And we calculated the encapsulation efficiency, the equilibrium constant between aqueous solutions and micelles, and the Gibbs free energy of partition at different concentrations of iron (Ⅱ, Ⅲ) oxide nanoparticles and different DP of hydrophobic segments. Experimental results show that CMC decreases with increasing concentrations of iron oxide nanoparticles and DP of hydrophobic segments. Average particle size of diblock copolymer micelles increases as concentrations of iron oxide nanoparticles and DP of hydrophobic segments increases. And the power-law exponents (n0) for natural logarithm of CMC versus the concentrations of iron oxide nanoparticles and the power-law exponents (n) for the average particle size of micelles versus the concentrations of iron oxide nanoparticles decrease with increasing DP of hydrophobic segments. The encapsulation efficiency of iron oxide nanoparticles and the equilibrium constant increase with increasing DP of hydrophobic segment but decreases with increasing concentrations of iron oxide nanoparticles. The absolute value of Gibbs free energy of partition (negative value) increases with concentrations of iron oxide nanoparticles but decreases with increasing DP of hydrophobic segments. From the results we find when the concentrations of iron oxide nanoparticles increases the absolute value of Gibbs free energy of micellization also increases, whereas the Gibbs free energy of partition decreases. It means the concentrations of iron oxide nanoparticles has an opposite effect on copolymer assembly and iron oxide nanoparticles assembly.