Positioning of Cubic Shaped Particles with Different Edge Structures in Nematic Medium

Öz

Liquid crystals (LC) are phases of matter that possess long range orientational order while maintaining fluidic properties. LCs have been shown to provide a medium that result in self-assembly of the colloidal particles through elastic interactions. One parameter that affects the positioning of the particles in LC medium is the edge sharpness of the particles. Simulation studies in the literature suggests that the edge sharpness of the particles directly affect the LC director profile at the vicinity of the particles, and playing a critical role in the formation and the shapes of the topological defects. This study provides a systematic study to show the effects of the edge sharpness on the orientation and the defect structure around the cubic shaped particles. The particles were shown to orient with their diagonal preferably parallel to the direction of the far field nematic director when the particles mediate planar anchoring. Whereas the particles with homeotropic anchoring did not exhibit strong preference in their orientation. We also showed defect structures to form around the particles with homeotropic surface anchoring. The defect structure around the particles with round edges were ring shaped, whereas the defects with S-shapes were formed around sharp-edged or truncated particles. The findings herein were found to be consistent with the simulations present in literature. The findings would find use in next generation materials for optics, photonics and responsive systems.

Anahtar Kelimeler

• Liquid crystals
• colloids
• alignment
• defects

Destekleyen Kurum

Scientific and Technological Research Council of Turkey (TÜBİTAK)

Proje Numarası

116C093

Teşekkür

The authors thank the financial support provided by Scientific and Technological Research Council of Turkey (TÜBİTAK) under award number 116C093.

Kaynakça

1. de Gennes, P. G., Prost, J., The Physics of Liquid Crystals; Second Edi, Oxford, New York, 1993.
2. Bukusoglu, E., Bedolla-Pantoja, M. A., Mushenheim, P. C., Wang, X., Abbott, N. L. 2016. Design of responsive and active (Soft) materials using liquid crystals. Annual Review of Chemical and Biomolecular Engineering; 7: 163–196.
3. Bai, Y., Abbott, N. L. 2011. Recent advances in colloidal and interfacial phenomena involving liquid crystals. Langmuir; 7: 5719–5738.
4. Loudet, J. C., Barois, P., Poulin, P. 2000. Colloidal ordering from phase separation in a liquid-crystalline continuous phase. Nature; 407: 611–613.
5. Mondiot, F., Chandran, S. P., Mondain-Monval, O., Loudet, J. C. 2009. Shape-induced dispersion of colloids in anisotropic fluids. Physical Review Letters: 103: 1–4.
6. Chandran, P. S., Mondiot, F., Mondain-Monval, O., Loudet, J. C. 2011. Photonic control of surface anchoring on solid colloids dispersed in liquid crystals. Langmuir; 27: 15185–15198.
7. Poulin, P., Weitz, D. A. 1998. Inverted and multiple nematic emulsions. Physical Review E; 57: 626–637.
8. Yuan, Y., Martinez, A., Senyuk, B., Tasinkevych, M., Smalyukh, I. I. 2018. Chiral liquid crystal colloids. Nature Materials; 17: 71–78.

9. Lapointe, C. P., Mason, T. G., Smalyukh, I. I. 2009. Shape-controlled colloidal interactions in nematic liquid crystals. Science; 326: 1083–1086.
10. Senyuk, B., Liu, Q., Bililign, E., Nystrom, P. D., Smalyukh, I. I. 2015. Geometry-guided colloidal interactions and self-tiling of elastic dipoles formed by truncated pyramid particles in liquid crystals. Physical Review E; 91: 1–8.
11. Yuan, Y., Liu, Q., Senyuk, B., Smalyukh, I. I. 2019. Elastic colloidal monopoles and reconfigurable self-assembly in liquid crystals Nature; 570: 214–218.
12. Wood, T. A., Lintuvuori, J. S., Schofield, A. B., Marenduzzo, D., Poon, W. C. K. 2014. A Self-Quenched Defect Glass in a Colloid-Nematic Liquid Crystal Composite. Science; 79: 79–83.
13. Koenig, G. M., de Pablo, J. J., Abbott, N. L. 2009. Characterization of the reversible interaction of pairs of nanoparticles dispersed in nematic liquid crystals. Langmuir; 25: 13318–13321.
14. Rahimi, M., Roberts, T. F., Armas-Pérez, J. C., Wang, X., Bukusoglu, E., Abbott, N. L., de Pablo, J. J. 2015. Nanoparticle self-assembly at the interface of liquid crystal droplets. Proceedings of the National Academy of the Sciences of the U. S. A.; 112: 5297–5302.
15. Wang, X., Miller, D. S., de Pablo, J. J., Abbott, N. L. 2014. Organized assemblies of colloids formed at the poles of micrometer-sized droplets of liquid crystal. Soft Matter; 10: 8821–8.
16. Wang, X., Miller, D. S., De Pablo, J. J., Abbott, N. L. 2014. Reversible switching of liquid crystalline order permits synthesis of homogeneous populations of dipolar patchy microparticles. Advanced Functional Materials; 24: 6219–6226.
17. Muševič, I., Škarabot, M., Tkalec, U., Ravnik, M., Žumer, S. 2006. Two-dimensional nematic colloidal crystals self-assembled by topological defects. Science; 313: 954–958.
18. Lapointe, C. P., Mayoral, K., Mason, T. G. 2013. Star colloids in nematic liquid crystals. Soft Matter; 9: 7843.
19. Lapointe, C., Hultgren, A., Silevitch, D. M., Felton, E. J., Reich, D. H., Leheny, R. L. 2004. Elastic Torque and the Levitation of Metal Wires by a Nematic Liquid Crystal. Science; 303: 652–655.
20. Hung, F. R., Bale, S. 2009. Faceted nanoparticles in a nematic liquid crystal: defect structures and potentials of mean force. Molecular Simulation; 35: 822–834.
21. Beller, D. A., Gharbi, A., Liu, I. B. 2015. Shape-controlled orientation and assembly of colloids with sharp edges in nematic liquid crystals. Soft Matter; 11: 1078–1086.
22. Miller, D. S., Carlton, R. J., Mushenheim, P. C., Abbott, N. L. 2013. Introduction to optical methods for characterizing liquid crystals at interfaces. Langmuir; 29: 3154–3169.