404190 Dodecagonal Quasicrystalline Morphology in a Poly(styrene-b-isoprene-b-styrene-b-ethylene oxide) Tetrablock Terpolymer

Monday, November 9, 2015: 5:00 PM
251D (Salt Palace Convention Center)
Jingwen Zhang, Product Fundamentals, ExxonMobil Chemical Company, Baytown, TX and Frank S. Bates, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN

A dodecagonal quasicrystalline (QC) morphology is identified in a poly(styrene-b-isoprene-b-styrene-b-ethylene oxide) (SISO) tetrablock terpolymer based on evidience provided by transimission electron microscopy (TEM), small-angle x-ray scattering (SAXS), and dynamic mechanical spectroscopy measurements. The QC state occurs at temperatures between those associated with hexagonal order (HEX) and the sigma-phase, THEX<TQC<Tσ<TODT, where TODT is the order-disorder transition temperature. All three morphologies are formed from spherical domains containing an O core surrounded by a shell of S that screens unfavorable segment-segment interactions within an I-rich matrix. TEM analysis reveals a QC morphology with 12-fold rotational symmetry but devoid of long-range translational order, along with locally cooridnated structures consistent with dodecagonal quasicrystalline approximates. The SISO molecular structure decouples control over the domain shape and interdomain interactions, leading to a multiplicity of packing symmetries.

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