Thursday, November 01, 2018
4:00 PM - 5:00 PM
Spalding Laboratory 106 (Hartley Memorial Seminar Room)

Chemical Engineering Seminar

Sphericity and Symmetry Breaking in Asymmetric Diblock Copolymer Melts
Frank Bates, Regents Professor, Chemical Engineering and Materials Science, University of Minnesota,
Speaker's Bio:
Frank S. Bates is a Regents Professor and a member of the Chemical Engineering and Materials Science department at the University of Minnesota. He received a B.S. in Mathematics from SUNY Albany and M.S. and Sc.D. degrees in Chemical Engineering from MIT. Between 1982 and 1989 Bates was a member of the technical staff at AT&T Bell Laboratories then joined the University of Minnesota where he served as department Head from 1999 to 2014. Bates conducts research on a range of topics related to polymers, with a particular focus on the thermodynamics and dynamics of block polymers, blends and solutions. He is a member of the National Academy of Engineering and the National Academy of Sciences, and the American Academy of Arts and Sciences.

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.