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

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, T_HEX<T_QC<T_σ<T_ODT, where T_ODT 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.