Abstract
Bent-core liquid crystals showing a nematic phase stable at low temperatures are very attractive for applicative purposes in view of the inherent biaxial nature of the nematic phase. In this work, a typical five-ring bent-core mesogen was investigated by means of 2H NMR spectroscopy and X-ray diffraction (XRD) methods. These techniques provide complementary information on the structural properties of the nematic phase and the average mesogen conformation: small-angle XRD reveals the presence of short-range positional order in the form of skewed cybotaxis, while a comparison of the orientational order parameters measured by wide-angle XRD and NMR provides an estimate of the molecule bend angle. In addition, 2H NMR puts in evidence the occurrence of an unexpected transition to a low-temperature tilted phase, having a crystalline or smectic-like character. The results were compared with those of previous 13C NMR investigations.
Highlights
Bent-core liquid crystals (BLCs) were first discovered in 1996 [1], and they are still very attractive for fundamental scientific reasons and for their potential applications, as demonstrated by very recent works [2,3,4]
The biaxial symmetry of the molecular arrangement of nematic phases formed by BLCs was induced by the presence of electric fields; in others, an extraordinary phase sensitivity to magnetic fields was observed [12,13,14]
Additional 2H NMR studies on molecular probes having nanosized ordered domains, or clusters, in the isotropic and in the nematic phase formed by this type of a similar structure than the BLC aromatic core, dissolved in different
Summary
Bent-core liquid crystals (BLCs) were first discovered in 1996 [1], and they are still very attractive for fundamental scientific reasons and for their potential applications, as demonstrated by very recent works [2,3,4]. The accepted model of the biaxial ‘cybotactic nematic’ phase assumes the existence of a peculiar short-range ordering in the structure in nematic domains, which, in BLCs, is not due to pre-transitional local fluctuations in the form of nanometer-sized clusters having a layered supramolecular structure Additional 2H NMR studies on molecular probes having nanosized ordered domains, or clusters, in the isotropic and in the nematic phase formed by this type of a similar structure than the BLC aromatic core (five- or three-rings moieties), dissolved in different. NMR main orientational and dynamic properties of nematic phases of typical calamitic LCs and five-rings spectroscopy has been used to investigate the mesophase biaxiality in several types of LC systems bent-core liquid crystals were compared [30,31]. An unexpected transition to a low temperature tilted phase, probably crystalline or smectic-like
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
