Orientation ordering in mesogens as an effect of backbone alignment

Wen-Jong Ma^1,2*, Leng-Wei Huang^2,3, Shih-Chieh Wang^2,4, Jan Busa Jr.^2,5, Natalia Tomašovičová⁶, Milan Timko⁶, Peter Kopcansky⁶, Katarina Siposova⁶, Chin-Kun Hu^2,7

¹Graduate Insitute of Applied Physics, National Chengchi University, Taipei, Taiwan
²Institute of Physics, Academia Sinica, Taipei, Taiwan
³Department of Physics, National Taiwan Normal University, Taipei, Taiwan
⁴Advanced Institute for Computational Science, RIKEN, Chuo-ku, Kobe, Japan
⁵Department of Mathematics and Theoretical Informatics,FEE&I, Technical University of Kosice, Kosice, Slovak Republic
⁶Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovak Republic
⁷Department of Physics, National Dong-Hwa University, Hua-Lian, Taiwan

* Presenter:Wen-Jong Ma, email:mwj@nccu.edu.tw

Orientation ordering underlies the major features of liquid crystal materials. Collections of biological molecules often stay in an orientation-ordered situation, which may not be perfectly long-ranged. In this study, we design a pathway to prepare orientation-ordered states for systems of mesogens modelled by stiff free-joint chains. On account of the fact that a system of stiff homogeneous chains often show strong tendency to collectively align into orientation-ordered domains in the two-phase coexistence region of the phase diagram, a dynamic procedure starting from an ordered configuration prepared after applying an auxiliary external field in that region, can be carried out to reach ordered or disordered final states for a variety of systems of non-homogeneous chains. The latter systems are reached from the original system of homogenous chains by tuning across the space of interaction parameters. The approach avoids the difficulty of requiring long relaxation times in conventional equilibrium simulations in which orientation-ordered states are obtained by starting from disordered configurations. By specifying the spatial extents over which the orders are effective, we can refine in a quantitative manner the varieties of ordering, which may or may not be long-ranged, obtained by carrying out the dynamic procedure.

Keywords: liquid crystal, orientation, ordering, coexistence, polymer