Spring Chem501 Seminar
UT Host: Dr. Michael Kilbey
Speaker: Dr. Mahesh Mahanthappa
Professor-Department of Chemical engineering & Materials Science
University of Minnesota
Title: “Molecular Frustration, Soft Quasicrystal Approximants, and the Escape to Infinity”
Abstract: Minimally hydrated amphiphiles self assemble into lyotropic liquid crystals (LLCs), which exhibit periodic aqueous and hydrophobic nanodomains. Commonly observed lyotropic mesophases include 1D lamellae, 2D columnar phases, 3D bicontinuous networks, and high symmetry 3D sphere packings. Based on hard sphere packings, spherical micelles are intuitively anticipated to form high symmetry body-centered cubic, face-centered cubic, and hexagonally close-packed structures. However, we recently discovered that ionic surfactant micelles also spontaneously form low symmetry, tetrahedrally close-packed Frank-Kasper σ and A15 phases, and related C14 and C15 Laves phases, with gigantic unit cells that mirror the structures of well-known intermetallic compounds. These new, low symmetry phases arise from a frustrated non-covalent force balance that minimizes local variations in amphiphile solvation, while maximizing global micelle cohesion within the particle ensemble. We discuss how chemical features of the surfactants and their path-dependent processing drive lyotropic sphere packing symmetry selection to yield complex assemblies. This work suggests that molecular engineering of frustration at competing length scales drives high fidelity, periodic pattern formation at length scales that far exceed those of their constituent molecular and supramolecular building blocks.
Bio: Mahesh K. Mahanthappa received his B.A. in Chemistry and Mathematics at the University of Colorado in 1997, and his Ph.D. in organometallic catalysis with Professor R. M. Waymouth at Stanford University in 2003. After postdoctoral studies with Professors F. S. Bates and M. A. Hillmyer from 2003–2006, he joined the Chemistry faculty of the University of Wisconsin–Madison in 2006. In 2015, Mahesh joined the faculty in the Department of Chemical Engineering & Materials Science at the University of Minnesota and was promoted to Full Professor in 2019.
The Mahanthappa group leverages chemical synthesis and materials characterization to identify new methods for manipulating block copolymer and lyotropic liquid crystal self-assembly into unique morphologies that manifest unusual bulk properties. He has received an NSF CAREER Award, a 3M Non-Tenured Faculty Award, the Emil H. Steiger Distinguished Teaching Award at UW-Madison, and the 2013 American Physical Society Dillon Medal in Polymer Physics.
Thursday, January 30, 2020 at 3:45pm to 5:00pm
Buehler Hall, 555
1420 Circle Drive, Knoxville, TN 37996