Microphase separation and molecular conformation of AB2 miktoarm star copolymers by dissipative particle dynamics

• Published in: Polymer (Guilford) Vol. 48; no. 15; pp. 4537 - 4546
• Main Authors: Huang, Ching-I., Yu, Hsu-Tung
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 13.07.2007; Elsevier
• Subjects: Applied sciences; Dissipative particle dynamics; Exact sciences and technology; Microphase separation; Miktoarm star copolymers; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties; Microphase separation; Dissipative particle dynamics; Miktoarm star copolymers; Star copolymer; Computer simulation; Phase diagram; Theoretical study; Composition effect; Radius of gyration; Order disorder transformation; Block copolymer; Conformation
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2007.06.002

We simulate the microphase separation behavior and analyze the molecular conformation of AB2 miktoarm star copolymers via dissipative particle dynamics (DPD). The phase diagram is constructed by varying the composition and interaction parameter. Through a mapping of the interaction parameter for a finite chain length, we find that the phase diagram via DPD is in near quantitative agreement with that predicted by the self-consistent mean-field (SCMF) theory. However, when the B composition is small, AB2 is not able to form the ordered microstructure as easily as SCMF has predicted. Instead, only a tube-like phase is formed. This aggregated micelle-like phase via DPD, which is ignored in the SCMF study, has been frequently observed in experiments. In the analysis of the radius of gyration (Rg), when the interaction parameter increases, the Rg values of each A and B arm remain relatively unchanged; while the overall radius of gyration of AB2 significantly increases. Furthermore, the angle between A and B arms shows an increasing trend while the angle between B and B arms shows a decreasing behavior with the interaction parameter. These results reveal that in order to reduce the contacts between A and B, the A and B arms tend to separate from each other, and the two B arms are squeezed onto the same side.