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10. de Vries Smectic Phases |
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We study a class of liquid crystals which shows 1% layer contractions [4] without any coordinated molecular tilt, known as deVries smectics. The materials used has an organosiloxane end-group and 5-phenylpyrimidine core and was recently reported as having a maximum 1.6% layer contraction. Small-angle x-ray study performed at MuCAT employed a ~0.5T magnetic field to induce alignment of the nematic director. The sample showed a 1% layer shrinkage and a relatively low orientational order parameter in comparison with the conventional SmA phase. Generally, the conventional SmA phase has S ~ 0.7 - 0.8, but the deVries SmA phase in this compound has S = 0.48. The large angle peak from a monodomain sample reveals a jump in and sharpening of the large angle peak at the transition to the SmC phase, supporting the diffuse cone model.
Figure. X-ray diffraction patterns and azimuthal diffraction profiles for small- and large- angle diffraction peak. After transition to SmC phase, a large angle diffraction peak shifted with an angle and the angle increased with decreasing temperature. |
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1. Origin of weak layer contraction in de Vries smectic liquid crystals, D. Agra-Kooijman, H-G. Yoon, S. Dey and S. Kumar, PRE 89, 032506 (2014). 2. Unraveling the Mystery of de Vries Smectic Phases, S. Kumar, Plenary Talk, 25th ILCC, Trinity College, Dublin, Ireland (2014). 3. The Orientational Distribution Function of de Vries Smectics (Poster), D. M. Agra-Kooijman, G. Singh, L. Sharpnack, Satyen Kumar. , 25th ILCC, Trinity College, Dublin, Ireland (2014). 4. Diffuse Cone Behavior and Microscopic Structure of the de Vries Smectic-A and Sm-C Phases, H.-G. Yoon, D. M. Agra-Kooijman, K. Ayub, R. P. Lemieux, and S. Kumar, Proceedings SPIE 8114, 811400 (2011). 5. Direct Observation of Diffuse Cone Behavior in de Vries Smectic-A and -C Phases of Organosiloxane Mesogens, H-G. Yoon, D. M. Agra-Kooijman, K. Ayub, R. P. Lemieux, and S. Kumar, Phys. Rev. Lett. 106, 087801 (2011). 6. Submolecular Organization and Diffuse Cone Behavior in a de Vries Smectic System, D. M. Agra-Kooijman, H-G. Yoon, K. Ayub, R. P. Lemieux, and S. Kumar, Gordon Research Conference: Liquid Crystals, South Hadley, MA, June 19-24, 2011. 7. Diffuse Cone Behavior in a de Vries-type Mesogen with 5-Phenylpyrimidine Core and Organosiloxane Chain, H.-G. Yoon, D. M. Agra-Kooijman, K. Ayub, R. P. Lemieux, and S. Kumar, Oral Presentation, 23rd International Liquid Crystal Conference, Krakow, Poland, July 11–16 (2010). 8. First direct evidence of diffuse-cone behavior at the SmA to SmC transition in a “deVries-like” organosiloxane mesogen with 5‑phenylpyrimidine Core, H.-G. Yoon, R. P. Lemieux, and S. Kumar, Synposium on “Anisotropic Soft Matter in bulk and under Confinement: Challenges in Integrating Theory, Simulations and Experiments”, Georgia Institute of Tech, Atlanta, Jan 28-29 (2010). |
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Publication/s and Presentations |
