Role of Chain Length in the Formation of Frank-Kasper Phases in Diblock Copolymers

ORAL

Abstract

Formation of the Frank-Kasper (FK) sigma phase in compositionally asymmetric A-B diblock copolymer melts has been shown using self-consistent mean-field theory (SCFT) to be associated with conformational asymmetry, bA/bB > 1, where b is the statistical segment length. Small-angle X-ray scattering and rheological measurements performed with narrow dispersity poly(styrene)-b-poly(butadiene) (PS-PB) diblocks show an absence of the FK sigma phase whereas poly(ethylethylene)-b-poly(lactide) (PEE-PLA) diblocks exhibit a wide composition window of this complex phase, where both systems have bA/bB = 1.3. This behavior is associated with block self-concentration expressed through the invariant degree of polymerization N(bar) = Nb6/v2 in which v is the statistical segment volume. A direct analogy will be drawn between the role of N(bar) in FK phase formation in diblocks and the value Ne(bar) that defines the universal crossover from Rouse to reptation dynamics in homopolymer melts, where the block values of N(bar) for PEE-PLA and PS-PB are less than and greater than Ne(bar), respectively.

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Presenters

  • Frank Bates

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

Authors

  • Frank Bates

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

  • Ronald Lewis III

    University of Minnesota

  • Akash Arora

    University of Minnesota

  • Haley Beech

    University of Minnesota

  • Bongjoon Lee

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

  • Aaron Lindsay

    University of Minnesota, University of Minnesota - Twin Cities

  • Timothy Lodge

    University of Minnesota, Department of Chemistry, University of Minnesota, Twin Cities, University of Minnesota - Twin Cities, Chemistry, University of Minnesota, Department of Chemistry, University of Minnesota

  • Kevin Dorfman

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