| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 95 === In this work, the dissipative particle dynamics (DPD) is employed to investigate the micellar morphologies formed by blockarm star copolymers. The work can be divided into three parts. The first is the study of a single diblock star copolymer (BmAn) in the mixed solvents which consists of common good solvent and water, selective solvent of A. Initially, the star expands freely in the common solvent, and then the solvophobic B-blocks start to shrink as water is added into the system. However, no sudden collapse of the solvophobic B-core is observed. The radius of gyration of the B-core decreases continuously as the water content (xw) increases. We have also found that for the single star copolymer solution, changes of the length of the solvophilic A-blocks have no effect on the size of the solvophobic core. For a system of multiple diblockarm star copolymers in the mixed solvents, there exist a minimum water content (xw,min) as well as a maximum water content (xw,max). When below minimum water content, stars tend to disperse freely within the solution and stars start to form micelles for xw>xw,min. The aggregation number of the micelle increases as water content increases and reaches a limiting value for xw>xw,max. Our simulation results indicate that the number of arms on a star seem to have no effect on xw,min and xw,max.
Second part of the work deals with the effect of the structures of the diblock star copolymers on the micellar morphologies in purely selective solvent. For the same polymeric volume fraction (
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