Abstract
Modulated nematic liquid crystal phases, which lack positional order but have some periodic variation in the direction of average orientation present in a classical nematic, have attracted significant interest. In the recently discovered splay nematic (NS) phase the average orientational order is augmented with a periodic splay deformation of orientation perpendicular to the director. We use X-ray scattering experiments to measure the orientational order parameters in the nematic (N) and splay nematic (NS) phases of the liquid crystalline material RM734. The degree of orientational order is somewhat larger in the NS phase than in the preceding nematic and temperature dependent. We reconstruct the orientational distribution function and find it to be nematic-like in the NS phase, indicating the change in orientation between neighbouring molecules due to the splay modulation is very small. A small splay angle implies that the splay modulation period is larger than the few tens of nanometers originally envisaged. The method described herein can be used to assist in unambiguous identification of the splay-nematic phase.
Highlights
Nematic liquid crystal phases, in which there is an average orientational order of the molecules but a lack of positional order, are the cornerstone of the display industry
As discussed in an earlier paper, when studied by X-ray scattering experiments the wide-angle peak RM734 is found over a large angular range and can be deconvoluted into two overlapping peaks (Fig. 2c) at 1.14 ÅÀ1 and 1.49 ÅÀ1. This is behaviour is observed in the NS phase, and in the nematic and isotropic liquid. If both wide-angle peaks originate from a single molecule the analysis presented in eqn (1)–(3) can still be used, whereas if one of the peaks originates from local phase biaxiality in the NS phase this approach may no longer be valid
That the two wide angle peaks are observed in the isotropic liquid and both nematic phases are strong indicators that they do not originate from biaxial local order, we sought further demonstration that these originate from the molecular shape of RM734 by calculating the molecular form factor (Fig. 2a) and scattered intensity profile (Fig. 2b)
Summary
In which there is an average orientational order of the molecules but a lack of positional order, are the cornerstone of the display industry. We use X-ray scattering experiments to measure the orientational order parameters in the nematic (N) and splay nematic (NS) phases of the liquid crystalline material RM734.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
