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Chemical Engineering Seminar

Thursday, November 1, 2018
4:00pm to 5:00pm
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Spalding Laboratory 106 (Hartley Memorial Seminar Room)
Sphericity and Symmetry Breaking in Asymmetric Diblock Copolymer Melts
Frank Bates, Regents Professor, Chemical Engineering and Materials Science, University of Minnesota,

Block polymers have captured the interest of scientists and engineers for more than half a century. In general, the phase behavior of A-B diblock copolymers, the simplest category of such self-assembling macromolecules, has been accepted as thoroughly understood. Recent experiments with low molecular weight diblock copolymers have revealed remarkable phase complexity in the limit of asymmetric compositions, 0.15 < fA < 0.25, where fA signifies the volume fraction of the minority block. Small-angle x-ray scattering (SAXS) measurements conducted in the vicinity of the order-disorder transition (ODT) temperature have revealed the formation of various low symmetry Frank-Kasper phases and a dodecagonal quasicrystal as a function of thermal processing history. Remarkably, when heated above the ODT temperature the liquid micelles retain a memory of the ordered state, which returns upon cooling. These finding will be discussed in the context of a competition between the tendency to form spherical micelles and the constraints associated with filing space at uniform density.

For more information, please contact Sohee Lee by phone at 6263954193 or by email at [email protected].