We demonstrate subnanometer resolution cryo-TEM imaging of smectic layers in the smectic and nematic phases of two bent-core liquid crystals. Our results show perfect periodicity over several hundred layers in the smectic phase and also provide the first direct evidence of smectic clusters on length scales of 30-50 nm in a nematic liquid crystal. The results are corroborated with small angle x-ray scattering measurements. The observation of smectic clusters in the nematic phase is of special interest in bent-core liquid crystals, where the smectic clusters are stable over wide temperature ranges, in contrast to the well-known pretransitional "cybotactic" clusters that appear only in the vicinity of a bulk smectic phase. The means to characterize and manipulate this nanoscale molecular order could open up completely new liquid crystal-based technologies.
Physical Review Letters
Copyright 2012 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevLett.109.107802.
Zhang, Cuiyu; Gao, Min; Weissflog, Wolfgang; Baumeister, Ute; Sprunt, Samuel N.; Gleeson, Jim T.; Jakli, Antal (2012). Direct Observation of Smectic Layers in Thermotropic Liquid Crystals. Physical Review Letters 109(10) Retrieved from https://oaks.kent.edu/cpippubs/66