Ph.D. University of Hull (UK), 1995
Liquid Crystal Synthesis, Development of New Synthetic Methodology, Asymmetric Synthesis, Heterocyclic Synthesis, Physical Analysis of Thermotropic Liquid Crystals
Research is primarily concerned with the synthesis of advanced liquid-crystalline materials for all-optical applications including for example, ferroelectric displays and optical interconnects for telecommunications transmission. The work is highly interdisciplinary and involves a unique blend of new methodology development targeted toward the synthesis of advanced liquid crystals and evaluation of the physical characteristics of the resulting mesogens (polarized optical microscopy, differential scanning calorimetry and electrooptic studies). A number of current projects are described in the following text:
De novo construction of new alkoxythiophene building blocks for liquid crystal synthesis. A prominent area of our research involves the synthesis of the elusive alkoxythiophene unit. Although this unit is a simple heterocycle, synthetic methodologies leading to the construction of these units are rare, low yielding, and often hazardous. We have developed a highly efficient synthesis of flexible alkoxythiophene units that are ideal precursors for the synthesis of thermotropic liquid crystals. Ring closure of appropriately substituted β-keto esters using Lawesson's reagent has been effected in both solvent-based and solvent free conditions (using microwave irradiation). We are currently using this chemistry in the synthesis of ferroelectric dopant and host materials for use in the latest portable, low-power display devices.
Construction of fluorinated thiophene units from fluorinated acyclic precursors. In collaboration with Paul Sampson's group we have been exploring the synthesis of fluorothiophenes from acyclic fluorinated dicarbonyl compounds. This chemistry represents the first potential pathway to fluorothiophenes using ring-closing methodology. The unique characteristics of low viscosity and high polarity of the fluorothiophene ring make these units ideal candidates for incorporation into calamitic structures with large negative dielectric anisotropy. Liquid crystals incorporating these units have been recently reported by our group and are some of the fastest ferroelectrics ever observed.
High birefringence materials for beam-steering applications. We have been involved in collaboration with Prof. S. T. Wu (University of Central Florida) for a number of years. We are concerned with the synthesis of materials having birefringences of over 0.5 and are particularly interested in compact mesogenic materials that contain highly polarizable elements. Our current focus is the synthesis of new hetereocylic units with unusual levels of conjugation.
Synthesis and evaluation of high chirality materials for use as asymmetric dopants in chiral nematic (cholesteric) display devices. Currently we are collaborating with Kent Displays Incorporated on the synthesis of new materials that are capable of conferring an extraordinarily high twisting power when placed in nematic host mixtures. We have received two NSF STTR grants and have submitted a full patent detailing the synthesis of such a material that is soluble, extremely robust, has a high twisting power (HTP), and confers a HTP that is constant over a wide operating temperature range!
Scholarly, Creative & Professional Activities
- Sybo, B., Bradley, P., Grubb, A., Miller, S., Proctor, K. J. W., Clowes, L., Lawrie, M. R., Sampson, P. & Seed, A. J. 1,3,4-Thiadiazole-2-carboxylate esters: New synthetic methodology for the preparation of an elusive family of self-organizing materials. Journal of Materials Chemistry 17, 3406-3411 (2007).
- Bradley, P., Sampson, P. & Seed, A. J. Preliminary communication: The synthesis of new mesogenic 1,3,4-thiadiazole-2-carboxylate esters via a novel ring closure. Liquid Crystals Today 14, 15-18 (2005).
- Seed, A. J., Walsh, M. E., Doane, J. W. & Khan, A. A new high twisting power material for use as a single asymmetric dopant in cholesteric displays with a temperature independence of the helical twisting power. Molecular Crystals and Liquid Crystals 410, 729-736 (2004).
- Gauza, S. et al. High birefringence isothiocyanato tolane liquid crystals. Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers 42, 3463-3466 (2003).
- Seed, A. J., Cross, G. J., Toyne, K. J. & Goodby, J. W. Novel, highly polarizable thiophene derivatives for use in nonlinear optical applications. Liquid Crystals 30, 1089-1107 (2003).
- Hirst, L. S.; Watson, S. J.; Gleeson, H. F.; Cluzeau, P.; Barois, P.; Pindak, R.; Pitney J.; Cady, A.; Johnson, P. M.; Huang, C. C.; Levelut, A.-M.; Srajer, G.; Pollmann, J.; Caliebe, W.; Seed, A.; Herbert, M. R.; Goodby, J.W. and Hird, M. Interlayer structures of the chiral smectic liquid crystal phases revealed by resonant x-ray scattering. Phys. Rev. E 65, 2002, article number 041705.
- Seed, A. J.; Sonpatki, V.; and Herbert,M. R. 3-(4-Bromobenzoyl)propanoic acid. Organic Syntheses 79, 2002, 204-208.
- Kiryanov, A. A.; Seed, A. J.; and Sampson, P. Synthesis and stability of 2-(1,1-difluoroalkyl) thiophenes and 1,1-difluoroalkyl benzenes: fluorinated building blocks for liquid crystal synthesis. Tetrahedron, 57, 2001, 5757-5767.
- Kiryanov, A. A.; Seed, A. J.; and Sampson, P. Ring fluorinated thiophenes: applications to liquid crystal synthesis. Tetrahedron Lett. 42, 2001, 8797-8800.
- Kiryanov, A. A.; Sampson, P. and Seed, A. J. Synthesis and mesomorphic properties of 1,1-difluoroalkyl-substituted biphenylthienyl and terphenyl liquid crystals. A comparative study of mesomorphic behavior relative to methylene, alkoxy and alkanoyl analogs. J. Mater. Chem. 11, 2001, 3068-3077.