Multiple Metastable Micellar States in Disordered Diblock Copolymers

ORAL

Abstract

Low molar mass and compositionally asymmetric polyisoprene-b-polylactide (PI-PLA) diblock copolymers were ordered into multiple crystalline states, including BCC and the σ, C14, and C15 Frank-Kasper phases, using recently discovered thermal processing techniques. For a given pre-ordered phase, heating above the order-disorder transition temperature (TODT) followed by cooling below TODT returns the system to the same ordered state. Small angle x-ray scattering revealed that the number density of micellar particles, n/V, is retained in the highly structured disordered liquid. We hypothesize that the number of micelles per volume, n/V, imprinted on the liquid during the initial ordering stage, governs the symmetry breaking during subsequent crystallization, and that the metastable structured liquid cannot achieve the equilibrium particle density due to prohibitively large free-energy barriers for micelle fusion and fission. Once the n/V is fixed, facile chain exchange redistributes mass to meet the required particle sizes and packing associated with individual ordered phases. This work reveals the nature of the fluctuating disordered state in asymmetric diblock copolymers in the low molar mass limit.

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Presenters

  • Kyungtae Kim

    Chemical Engineering and Materials Science, Univ of Minn - Minneapolis, Department of Chemical Engineering and Materials Science, University of Minnesota, Univ of Minnesota - Twin Cities

Authors

  • Kyungtae Kim

    Chemical Engineering and Materials Science, Univ of Minn - Minneapolis, Department of Chemical Engineering and Materials Science, University of Minnesota, Univ of Minnesota - Twin Cities

  • Akash Arora

    Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, Chemical Engineering and Materials Science, Univ of Minn - Minneapolis, Department of Chemical Engineering and Materials Science, University of Minnesota

  • Ronald Lewis

    Department of Chemical Engineering and Materials Science, University of Minnesota, Univ of Minnesota - Twin Cities

  • Meijiao Liu

    Department of Chemistry, Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Education Ministry, Zhejiang Sci-Tech University

  • Wei-hua Li

    Department of Macromolecular Science, Fudan Univ, Department of Macromolecular Science, Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University

  • Anchang Shi

    Department of Physics and Astronomy, McMaster University, Fudan Univ, Physics and Astronomy, McMaster University

  • Kevin Dorfman

    Chemical Engineering and Materials Science, Univ of Minn - Minneapolis, Department of Chemical Engineering and Material Science, University of Minnesota, Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, Department of Chemical Engineering and Materials Science, University of Minnesota

  • Frank Bates

    Univ of Minnesota - Twin Cities, Chemical Engineering and Materials Science, University of Minnesota - Twin Cities, Chemical Engineering and Materials Science, Univ of Minn - Minneapolis, Department of Chemical Engineering and Materials Science, University of Minnesota