A delicate balance of noncovalent interactions drives hydrated molecular amphiphile self-assembly into lyotropic liquid crystals (LLCs) of varied morphologies, with applications including nanoporous membranes, mesoporous material templates, and therapeutic delivery vehicles. Spherical micelles are intuitively anticipated to form high-symmetry close-packed and body-centered cubic (BCC) LLCs, by analogy to packings of “hard” (immutable) spheres. However, we have discovered that ionic surfactant micelles also form a variety of low-symmetry, tetrahedrally close-packed Frank–Kasper (FK) phases, each exhibiting discrete micelle size distributions. The spontaneous emergence of FK sigma, A15, C14, and C15 LLC phases arises from a frustrated noncovalent force balance that minimizes variations in amphiphile solvation, while maximizing electrostatic cohesion in the ionic micelle ensemble. We further describe how amphiphile structure and path-dependent processing of their aqueous dispersions drive LLC sphere packing symmetry selection, culminating in the discovery of aperiodically ordered lyotropic dodecagonal quasicrystals (DDQCs) in multiple amphiphile systems. Thus, these findings establish the ubiquity of complex (a)periodically ordered states in both hard and soft materials and suggest methods for producing them at larger length scales.

Bio:

Mahesh Mahanthappa received B.A. degrees in Chemistry & Mathematics at the University of Colorado–Boulder in 1997, and a Ph.D. in organometallic catalysis with Professor R. M. Waymouth as a Hertz Fellow at Stanford University in 2003. After postdoctoral studies with Professors F. S. Bates and M. A. Hillmyer at University of Minnesota (2003–2006), he joined the Chemistry faculty of the University of Wisconsin–Madison in 2006. In 2015, Mahesh moved to the Department of Chemical Engineering & Materials Science at the University of Minnesota, where he 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 with unusual bulk properties. Mahesh has received various awards for research and teaching, including the 2013 American Physical Society Dillon Medal in Polymer Physics, the Emil H. Steiger Chancellor’s Distinguished Teaching Award at UW-Madison, and the 2020 American Chemical Society Division of Chemical Health & Safety Graduate Research Faculty Safety Award. He is a Kavli Foundation Fellow and a Fellow of the American Physical Society.