Micellar Morphologies formed by Triblock Copolymers in Mixed Solvents: A Dissiptative Particle Dynamics Simulation Approach
Date Issued
2007
Date
2007
Author(s)
Cheng, Yu-Wen
DOI
zh-TW
Abstract
In this work, we have investigated the morphologies of triblock copolymer in mixed solvents by using dissipative particle dynamics. The triblock copolymer consists of A, B and C blocks, which is hydrophilic, weakly hydrophobic and strongly hydrophobic. According to the work of Einsenberg, different micellar morphologies can be observed for diblock copolymers by adding different amount of selective solvent (water) in common solvents (dioxane and DMF). Here we focus our attention in studying how the morphologies of the aggregates evolve as water content increases. We have also estimated in our simulation the intensity of small angel neutron scattering of the system to identify change of states of micellar formation.
Linear and star ABC triblock copolymers with two hydrophobic blocks and one hydrophilic block are examined in this work. It is found that critical water content (cwc), which is the water content for the first micelles to form, decreases as the volume fraction of polymer increases irrespective of the architecture of the triblock copolymer. Triblock copolymers with different architectures result in different micellar morphologies. For example, ABC triblock copolymers form typical core-shell-corona micelles and on the other hand, linear BAC as well as ABC star copolymers develop segmented-worm aggregates in purely selective solvents. For the same triblock copolymer, transformation between different morphologies can be observed as water content in the mixed solvent increases. Therefore we can tune the morphologies of copolymers by changing the solvent quality. It is also found that critical water content of the system is not affected by the length of the hydrophilic blocks. We have performed the calculation of the intensity of SANS in our simulation. Results show that sudden changes in the SANS consistently indicates transformations of the morphologies of micelles formed.
Subjects
三段鏈
混合溶劑
mixing solvents
triblock copolymer
morphology
Type
thesis