| Summary: | 碩士 === 國立臺灣科技大學 === 高分子工程系 === 91 === This work is to study the effect of the Poly(ethylene glycol)(PEG) block on the pore size of Poly(L-lactide)/PEG/ Poly(L-lactide)(PLLA/PEG/PLLA) membranes prepared by phase inversion method with methylene dichloride and ethyl alcohol. The pore size was found to increase with the length of PEG blocks, where this phase separation phenomenon was interpreted with the critical interaction parameters between PEG and PLLA blocks in the Leibler’s theory for block copolymers in the non-selective solvents. The polarizing microscopy measurements leads to the equilibrium melting temperatures and activities of PLLA crystallines phases in the prepared membranes, and the larges pore size corresponds with the less PLLA activity in which the PLLA chain in crystalline lamellae is less stretch. Also, the quasi-ternary phase equilibrium thermodynamics considering the crystallization show the relationship between polymer-solvent and polymer-nonsolvent interaction parameters with various nonsolvent fractions. It is concluded that the liquid-liquid separation mechanism, compared to crystallization is more favorable to the pore formation as accompanied with less PLLA activity, higher polymer-solvent interaction parameter, and higher critical interaction parameter for PLLA and PEG blocks to phase separate.
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