(184j) Faceted Nanoparticles in a Nematic Liquid Crystal: A Computational Study | AIChE

(184j) Faceted Nanoparticles in a Nematic Liquid Crystal: A Computational Study


Hung, F. R. - Presenter, Louisiana State University
Bale, S. - Presenter, Louisiana State University

We studied the defect structures, potentials of mean force (PMF) and torques that develop when faceted nanoparticles, namely cubes and triangular prisms, are immersed in a nematic liquid crystal. When the particles are introduced in the LC, they produce a distortion in its director field. Because of this distortion, the particles and the LC try to rearrange in order to minimize the elastic perturbation, which in turn leads to long range interparticle interactions that can induce the formation of a number of ordered colloid structures which have potential in applications in light-scattering devices, electro-optical switches, photonics, nanoscale electronics, LC displays and the development of optical sensors [1,2,3,4].

We used a mesoscale theory in terms of the tensor order parameter Q(r) to model the nematic liquid crystal. Most of the previous experimental work has dealt with spherical, micron sized particles in LC, therefore our results were compared with similar results for spherical particles of comparable sizes. Our results show [5] that for the case of two nanocubes, an additional disclination ring forms in the interparticle space, which leads to the development of strong, LC-mediated interactions between the cubic particles. For the case of two triangular nanoprisms, we considered three particle arrays: linear (the long axes of the particles are collinear and the particles have the same orientation), parallel (the long axes of the particles are parallel and the particles have the same orientation) and inverted parallel (the long axes of the particles are parallel, and one of the prisms is inverted with respect to the other one). Our results suggest that inverted parallel arrays are thermodynamically more stable than linear arrays, which in turn are more stable than parallel arrays. Our results indicate that the nematic-mediated interparticle interactions are highly directional and strong (up to ~1000 kT), and could be used to assemble the particles into ordered structures with different morphologies.

[1] P. Poulin, H. Stark, T. C. Lubensky and D. A. Weitz, Science 275, 1770 (1997); J. C. Loudet, P. Barois and P. Poulin, Nature 407, 611 (2000); J. C. Loudet and P. Poulin, Phys. Rev. Lett. 87, 165503 (2001) [2] M. Yada, J. Yamamoto and H. Yokoyama, Phys. Rev. Lett. 92, 185501 (2004) [3] A. B. Nych, U. M. Ognysta, V. M. Pergamenshchik, B. I. Lev, V. G. Nazarenko, I. Mu?evič, M. ?karabot and O. D. Lavrentovich, Phys. Rev. Lett. 98, 057801 (2007) [4] I. Mu?evič, M. ?karabot, U. Tkalec, M. Ravnik and S. ?umer, Science 313, 954 (2006); M. Ravnik, M. ?karabot, S. ?umer, U. Tkalec, I. Poberaj, D. Babič, N. Osterman and I. Mu?evič, Phys. Rev. Lett. 99, 247801 (2007); U. Tkalec, M. ?karabot, and I. Mu?evic, Soft Matter 4, 2402 (2008) [5] F. R. Hung, Phys. Rev. E 79, 021705 (2009); F. R. Hung and S. Bale, Mol. Simulat. 35, 822 (2009)