David Walba

Liquid Crystals, Polymers, and Gels, Materials Chirality, Electro-Optic Materials, Ferroelectric Liquid Crystals

Research in the Walba group focuses on supermolecular stereochemistry and materials chirality in the context of liquid crystal science and technology. Most projects in the group are interdisciplinary; runing in collaboration with CU students and Professors in the Physics. 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, creation of new liquid crystals for high resolution TV and holographic projector applications, development of new liquid crystals for organic photovoltaics applications, and exploration of new approaches for controlling liquid crystal macroscopic stereochemistry using novel liquid crystal/solid surface interfaces.

Ferroelectric liquid crystals represent a unique "soft matter" system 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 can form ferroelectric liquid crystals. More interestingly, these phases are chiral, even thought the molecules are achiral or racemic. 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 fluid phase.

Hu, N.; Shao, R.; Shen, Y.; Chen, D.; Clark, N. A.; Walba, D. M. "An electric-field-responsive discotic liquid-crystalline hexa-peri-hexabenzocoronene/oligothiophene hybrid," Adv. Mater. 2013, Early View

DOI: 10.1002/adma.201304371.

Tsai, E.; Richardson, J. M.; Korblova, E.; Nakata, M.; Chen, D.; Shen, Y.; Shao, R.; Clark, N. A.; Walba, D. M. "A modulated helical nanofilament phase," Angew. Chem. Int. Ed. 2013, 52, (20), 5254-7.

Kim, H.; Lee, S.; Shin, T. J.; Cha, Y. J.; Korblova, E.; Walba, D. M.; Clark, N. A.; Lee, S. B.; Yoon, D. K. "Alignment of helical nanofilaments on the surfaces of various self-assembled monolayers," Soft Matter 2013, 9, (26), 6185-6191.

Chen, D.; Porada, J. H.; Hooper, J. B.; Klittnick, A.; Shen, Y.; Tuchband, M. R.; Korblova, E.; Bedrov, D.; Walba, D. M.; Glaser, M. A.; Maclennan, J. E.; Clark, N. A. "Chiral heliconical ground state of nanoscale pitch in a nematic liquid crystal of achiral molecular dimers," Proceedings of the National Academy of Sciences 2013.

Chen, D.; Heberling, M.-S.; Nakata, M.; Hough, L. E.; Maclennan, J. E.; Glaser, M. A.; Korblova, E.; Walba, D. M.; Watanabe, J.; Clark, N. A. "Structure of the b4 liquid crystal phase near a glass surface," ChemPhysChem 2012, 13, (1), 155-159.

Reddy, R. A.; Zhu, C.; Shao, R.; Korblova, E.; Gong, T.; Shen, Y.; Garcia, E.; Glaser, M. A.; Maclennan, J. E.; Walba, D. M.; Clark, N. A. "Spontaneous ferroelectric order in a bent-core smectic liquid crystal of fluid orthorhombic layers," Science 2011, 332, 72-77.

Chen, D.; Maclennan, J. E.; Shao, R.; Yoon, D. K.; Wang, H.; Korblova, E.; Walba, D. M.; Glaser, M. A.; Clark, N. A. "Chirality-preserving growth of helical filaments in the b4 phase of bent-core liquid crystals," J. Am. Chem. Soc. 2011, 133, (32), 12656-12663.

Yang, H.; Richardson, J. M.; Walba, D. M.; Zhu, C.; Shao, R.; Clark, N. A.; Ortega, J.; Etxebarria, J.; Keller, P. "Synthesis and physical properties of a main-chain chiral smectic thiol-ene oligomer," Liq. Cryst. 2010, 37, (3), 325-334.

Walba, D. M.; Yang, H.; Keller, P.; Zhu, C.; Shao, R.; Coleman, D. A.; Jones, C. D.; Clark, N. A. "A main-chain de vries smectic liquid crystal polymer prepared by hoveyda–grubbs catalyst initiated acyclic diene metathesis polymerization," Macromol. Rapid Commun. 2009, 30, 1894-1899.

Hough, L. E.; Spannuth, M.; Nakata, M.; Coleman, D. A.; Jones, C. D.; Dantlgraber, G.; Tschierske, C.; Watanabe, J.; Korblova, E.; Walba, D. M.; Maclennan, J. E.; Glaser, M. A.; Clark, N. A. "Chiral isotropic liquids from achiral molecules," Science 2009, 325, (5939), 452-456.

Hough, L. E.; Jung, H. T.; Krüerke, D.; Heberling, M. S.; Nakata, M.; Jones, C. D.; Chen, D.; Link, D. R.; Zasadzinski, J.; Heppke, G.; Rabe, J. P.; Stocker, W.; Körblova, E.; Walba, D. M.; Glaser, M. A.; Clark, N. A. "Helical nanofilament phases," Science 2009, 325, (5939), 456-460.

Walba, D. M.; Yang, H.; Shoemaker, R. K.; Keller, P.; Shao, R.; Coleman, D. A.; Jones, C. D.; Nakata, M.; Clark, N. A. "Main-chain chiral smectic polymers showing a large electroclnic effect in the SmA* phase," Chem. Mater. 2006, ASAP Article; DOI: 10.1021/cm0606373.

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, 5318-5319.

Walba, D. M.; Eshdat, L.; Körblova, E.; Shoemaker, R. K. "On the nature of the B4 banana phase: Crystal or not a crystal?," Cryst. Growth Des. 2005, 5, 2091-2099.

Walba, D. M.; Xiao, L.; Korblova, E.; Keller, P.; Shoemaker, R.; Nakata, M.; Shao, R.; Link, D. R.; Coleman, D. A.; Clark, N. A. "Main-chain ferroelectric liquid crystal polymers for electronic nonlinear optics applications," Ferroelectrics 2004, 309, 77-82.

Coleman, D. A.; Fernsler, J.; Chattham, N.; Nakata, M.; Takanishi, Y.; Korblova, E.; Link, D. R.; Shao, R. F.; Jang, W. G.; Maclennan, J. E.; Mondainn-Monval, O.; Boyer, C.; Weissflog, W.; Pelzl, G.; Chien, L. C.; Zasadzinski, J.; Watanabe, J.; Walba, D. M.; Takezoe, H.; Clark, N. A. "Polarization-modulated smectic liquid crystal phases," Science 2003, 301, 1204-1211.

Walba, D.M.; Korblova, E.; Shao, R.; Maclennan, J.E.; Link, D.R.; Glaser, M.A.; Clark, N.A. "A ferroelectric liquid crystal conglomerate composed of racemic molecules," Science, 2000, 288, 2181-2184.

Link, D. R.; Natale, G.; Shao, R.; Maclennan, J. E.; Clark, N. A.; Korblova, E.; Walba, D. M. "Spontaneous formation of macroscopic chiral domains in a fluid smectic phase of achiral molecules," Science 1997, 278, 1924-1927.