Past Seminars Seminários Já Decorridos 2015

Recent developments in chiral nematics: band-gap broadening, reflection from dispersed droplets and wetting

By: Rafael Zola
From: Universidade Tecnológica Federal do Paraná
At: Faculdade de Ciências, Ed. C8, 8.2.06
[2015-04-23] 11:00

In this talk, some recent developments in the chiral nematic field will be presented. First, the photonic band-gap broadening in negative dielectric anisotropy, polymers stabilized chiral nematics is discussed. It will be shown how ionic interactions are responsible for the translation of polymer fibers, causing a non-homogenous distribution of the pitch. Then, I will show some results in a lattice of cholesteric colloidal particles. We used a micro fluidic technique to fabricate monodisperse, photo sensitive droplets embedded in a PVA aqueous solution. The lattice produces omnidirectional reflection of circularly polarized light and cross talk between neighbor drops. The reflection band can be controlled by UV and visible light and the Bragg reflection condition yields patterns under white light illumination. Last, some characteristics of the surface induced pattern formation in chiral nematics will be discussed. In a confined system, wetting strength, chirality, elastic anisotropy and surface anchoring compete for the formation and dynamics of stripes. The main results will be discussed.


[1] V. P. Tondiglia, L. V. Natarajan, C. A. Bailey, M. E. Mcconney, M. Lee, T. J Bunning ,H. Nemati, R. S. Zola, D.-Ke Yang and T. J White, Optical Materials Express, 24, 6260 (2014).

[2] H. Nemati, R. S. Zola, S. Liu, V. P Tondiglia, K. Lee, T. J. White, T. Bunning and  Deng-Ke Yang, Soft Matter, 11, 1208 (2015).

[3] J. Fan, Y. Li, H. K. Bisoyi, R. S. Zola, D.-Ke Yang, T. J. Bunning, D. A. Weitz and Q. Li, Angew. Chem. Int. Ed. 54, 2160 (2015).

[4] R. S. Zola, L. R. Evangelista, Y-C. Yang and D.-Ke Yang. Phys. Rev. Lett. 110, 057801 (2013).