Exploring ideality and reality in an archetypal rodlike nematic liquid crystal. Issue 13 (20th October 2020)

• Record Type: Journal Article
• Authors: Madsen, Louis A.; Dingemans, Theo J.; Poon, Chi-Duen; Samulski, Edward T.
• Is Part Of: Liquid crystals. Volume 47:Issue 13(2020)
• Page Start: 2027
• Page End: 2042
• Publication Date: 2020-10-20
• Subjects: Deuterium NMR -- molecular dynamics -- Maier-Saupe -- director fluctutations -- molecular flexibility; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2019.1662107
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: Numerous theories of molecular ordering in the nematic phase exist that attempt to incorporate the features of weak attractions, excluded volume (aspect ratio), and rigid and non-rigid segments, as well as assess entropic and enthalpic effects. Para -quinquephenyl represents a model rodlike molecule, but study of this liquid crystal presents challenges and surprises given the high temperature of the nematic phase. We present NMR experiments throughout the nematic range on two specifically deuterium-labelled quinquephenyl isotopomers, which we combine with high fidelity molecular dynamics simulations to explore and quantify various aspects of orientational order. The striking agreement between experiment and simulation provides new insights into the role of molecular flexibility and correlations (clustering, director fluctuations) on observed order parameters. We compare several nematic theories with our observations and discuss implications for further theoretical understanding. GRAPHICAL ABSTRACT: uf0001