Past Seminars Seminários Já Decorridos 2012

Electro-optical studies of visco-elastic and electrical properties in a nematic organo-siloxane tetrapode exhibiting a biaxial nematic phase

By: João Luis Figueirinhas
From: IST and CFMC
At: Instituto de Investigação Interdisciplinar, Anfiteatro
[2012-03-06] 11:30

Capacitance and optical measurements carried out with electric fields going above the Freedericksz threshold are used to determine the dielectric and relevant elastic constants controlling the director’s reorientation in both planar and homeotropic samples, through simulation of the underlying process. This technique which has been successfully applied to uniaxial nematics is used here to analyse also the temperature range where the NB phase was reported for this organo-siloxane tetrapode. The results are discussed in the context set by previous studies of phase biaxiality in this and similar compounds [1-4].

[1] K. Merkel, A. Kocot, J. K. Vij, R. Korlacki, G. H. Mehl and T. Meyer, Phys. Rev. Lett. 93, 237801 (2004).

[2] J. L. Figueirinhas, C. Cruz, D. Filip, G. Feio, A. C. Ribeiro, Y. Fre`re, T. Meyer and G. H.Mehl, Phys. Rev. Lett. 94, 107802 (2005).

[3] K. Neupane, S. W. Kang, S. Sharma, D. Carney, T. Meyer, G. H. Mehl, D. W. Allender, S.Kumar and S. Sprunt, Phys. Rev. Lett. 97, 207802 (2006).

[4] C. Tschierske, D. J. Photinos, J.Mater.Chem. 20, 4263, (2010).