Walba, D. M.; Eshdat, L.; Korblova, E.; Shao, R.; Clark, N. A. "A general method for measurement of enantiomeric excess by using electrooptics in ferroelectric liquid crystals," Angew. Chem. Int. Ed. 2007, 46, 1473-1475
Kane, A.; Shao, R.-F.; Maclennan, J. E.; Wang, L.; Walba, D. M.; Clark, N. A. "Electric-field-driven deracemization," ChemPhysChem 2007, 8, 170-174.
Walba, D. M.; Yang, H.; Shoemaker, R. K.; Keller, P.; Shao, R. F.; Coleman, D. A.; Jones, C. D.; Nakata, M.; Clark, N. A. "Main-chain chiral smectic polymers showing a large electroclinic effect in the SmA* phase," Chem. Mater. 2006, 18, (19), 4576-4584.
Walba, D. M.; Korblova, E.; Huang, C. C.; Shao, R. F.; Nakata, M.; Clark, N. A. "Reflection symmetry breaking in achiral rod-shaped smectic liquid crystals?," J. Am. Chem. Soc. 2006, 128, (16), 5318-5319.
Saipa, A.; Osipov, M. A.; Lanham, K. W.; Chang, C. H.; Walba, D. M.; Giesselmann, F. "The intrinsic photoferroelectric effect in the smectic C* phase of a chiral azobenzene," J. Mater. Chem. 2006, 16, (42), 4170-4177.
Lagerwall, J. P. F.; Coleman, D.; Korblova, E. K.; Jones, C.; Shao, R.; Oton, J. M.; Walba, D. M.; Clark, N.; Giesselmann, F. "The peculiar optic, dielectric and X-ray diffraction properties of a fluorinated de Vries asymmetric diffuse cone-model ferroelectric liquid crystal," Liq. Cryst. 2006, 33, (1), 17-23.
Jones, C. D.; Shao, R. F.; Rappaport, A. G.; MacLennan, J. E.; Clark, N. A.; Korblova, E.; Walba, D. M. "Director structures in achiral smectic C liquid crystal cells: field-induced twist domain nucleation," Liq. Cryst. 2006, 33, (1), 25-32.
Research in the Walba group focuses on organic stereochemistry in the context of liquid crystal science and technology. Most projects in the group are interdisciplinary; run in collaboration with CU Professors in the Physics and Chemical Engineering Departments. These include synthesis of molecules designed to provide new liquid crystal phases, design and synthesis of ferroelectric liquid crystals and polymers for nonlinear optics applications, development of computational approaches for understanding and predicting liquid crystal properties from molecular structure, and exploration of new approaches for controlling liquid crystal macroscopic stereochemistry using novel liquid crystal/solid surface interfaces.
Most of our work involves ferroelectric liquid crystals, which are unique fluids possessing polar symmetry and a spontaneous macroscopic electric dipole moment. One illustrative project involves synthesis and characterization of new banana phases, named after the shape of the molecules forming the phases. Until recently all ferroelectric liquid crystals were composed of enantiomerically enriched molecules. Recently, however, we have shown that achiral or racemic banana-shaped molecules (see Figure 1) can form ferroelectric liquid crystals. More interestingly, these phases are chiral, even thought the molecules are not. This is analogous to Pasteur's famous discovery of the macroscopic chirality of racemic tartrate crystals in the nineteenth century, but for the first time observed in a liquid.
Figure 1: Molecular structure of ferroelectric banana MHOBOW
A photomicrograph, taken with the liquid crystal sample between crossed polarizers, shows below (in Figure 2) the beautiful texture observed for one of the new phases of the racemic compound MHOBOW, the materialexhibiting the first ferroelectric banana phase.
Figure 2: Photomicrography of the first ferroelectric banana phase
