| Summary: | 碩士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 95 === We employ the dissipative particle dynamics (DPD) to examine the microphase separation and the molecular conformation behavior of A2-star-(B-alt-C) copolymers. We find that a hierachical structure with two length scales, i.e., the so-called structure-within-structure, can be successfully induced by grafting an alternating BC block into an A block. First, similar to the linear diblock copolymers, the immiscibility parameter between A and B/C plays a dominating role for the copolymers to form an ordered microstructure at large length scale. In addition to the composition, the interaction parameter between B and C, aBC, also has a great influence on the resulting morphology geometry. In particular, as aBC decreases, i.e., when B and C components become more attractive, the BC alternating block is likely to curl more. As a consequence, even for the copolymers with the A block as a minority component, the systems can undergo a series of microphase transition into the cylinders and spheres formed by the majority BC alternating block, i.e., the so-called inverted structures. Whereas, when aBC increases, a segregation between B and C can be induced inside the B/C-rich domains. Various structure-within-structures, such as , -within- , -within- , -within- , , and are observed by increasing the A composition.
In the analysis of molecular conformation, we observe that at a fixed interaction parameter between B and C, when the interaction parameter between A and B/C increases so that the systems transform from a disordered into an ordered state, the radius of gyration for each A and BC arm remains somewhat a constant; whereas the overall radius of gyration significantly increases. This manifests the fact that in order to reduce the contacts between A and BC, the angle between A and BC arms increases and the angle between A and A arms decreases.
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