ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

PhD Preliminary DefenseAmeer R.K. NassrahHUN-REN Wigner RCP 
SZFIPhotoalignment at Liquid Crystal–Polymer InterfaceTuesday, 6 February 
2024, 10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference RoomProper, 
controllable alignment of the liquid crystal (LC) molecules at solid 
substrates is a key factor for correct operation of all LC-based devices. 
Photoalignment is a promising, contactless method of achieving the required 
alignment, which can be applied in enclosed areas (e.g., in microfluidic 
channels), and which avoids the drawbacks of mechanical contacts (e.g., 
mechanical damages, accumulation of ions and dust particles). In these 
photoaligning systems, a very small number of photochromic derivatives 
anchored on a substrate commands the alignment of a very large number of LC 
molecules in contact with it, and therefore, the surfaces were referred to as 
“command surfaces”. The experiments were focusing on the influence of the LC 
molecular structure and that of the LC phase on the photoalignment process. 
The results indicate the importance of both the LC structure and the phase 
[1,2]. An interaction mechanism has been proposed between the command surface 
and the LC molecules for the peculiar photoalignment properties of LCs with 
biphenyl rigid core. The proposed interaction mechanism has been validated by 
additional experimental results [2]. The dependence of the photoalignment on 
the composition of the command surface has also been tested. Drastic 
differences have been found in the efficiency of the photoalignment depending 
on the preparation method. AFM measurements have shown, that efficient 
photoalignment is accompanied with a significant photo-induced mass transfer 
[3].[1] A.R.K. Nassrah, I. Jánossy and T. Tóth-Katona, “Photoalignment at the 
Nematic Liquid Crystal-Polymer Interface: The Importance of the Liquid 
Crystalline Molecular Structure.” J. Mol. Liq., 312, 113309/1-7 (2020). [2] 
A.R.K. Nassrah, I. Jánossy, V. Kenderesi, T. Tóth-Katona, “Polymer-Nematic 
Liquid Crystal Interface: On the Role of the Liquid Crystalline Molecular 
Structure and the Phase Sequence in Photoalignment.” Polymers 13, 193/1-13 
(2021). [3] A.R.K. Nassrah, M. Batkova, N. Tomašovičová, T. Tóth-Katona, 
“Photoaligning Polymeric Command Surfaces: Bind, or Mix?” Polymers 15, 
4271/1-12 (2023). Minden érdeklődőt szívesen látunk! - Everyone is 
welcome to attend.Attila Nagysem-admin AT szfki.hu