Abstract
Calamitic liquid crystals based on 5-phenyl-pyrimidine derivatives have been designed, synthesized, and characterized. The 5-phenyl pyrimidine core was functionalized with a chiral (R,R)-2,3-epoxyhexoxy chain on one side and either siloxane or perfluoro terminated chains on the opposite side. The one involving a perfluorinated chain shows phase over a wide temperature range of 82 °C, whereas the siloxane analog exhibits both and phases over a broad range of temperatures, and a weak first-order transition is observed. For the siloxane analog, the reduction factor for the layer shrinkage R (relative to its thickness at the transition temperature, ) is , and layer shrinkage is 1.7% at a temperature of 13 °C below the . This compound is considered to have “de Vries smectic” characteristics with the de Vries coefficient of ∼0.86 on the scale of zero (maximum-layer shrinkage) to 1 (zero-layer shrinkage). A three-parameter mean-field model is introduced for the orientational distribution function (ODF) to reproduce the electro-optic properties. This model explains the experimental results and leads to the ODF, which exhibits a crossover from the sugar-loaf to diffuse-cone ODF some 3 °C above .
14 More- Received 13 July 2017
- Revised 1 September 2017
DOI:https://doi.org/10.1103/PhysRevE.96.042701
©2017 American Physical Society