Cristais líquidos colestéricos: a quiralidade revela as suas cores

Abstract

Chirality deeply impacts the macroscopic properties on all scales of the universe from elemental particles through biological structures up to astronomic systems. Specifically, chiral liquid crystals give rise to self-organized macrostructures with unparalleled properties. Here we present easy experiments with a special class of chiral liquid crystals that show temperature-induced selective reflection of light (thermochromic effect). Understanding this thermochromic effect allows undergraduate students better realize important properties of super and supramolecular systems.

Enhancement of Photoluminescence Intensity of CdSe Nanorods Doped in Cholesteric Liquid Crystals

“…The presence of chiral molecules induces the LC directors to twist and rotate in a helical arrangement, forming a periodically layer-like structure. Such structure makes CLC behave as a one-dimensional photonic crystal and display valuable optical properties such as selective reflection [1]: the light possessing the same handedness as CLC helicity and the wavelength equal to the optical pitch of the CLC would be mostly reflected. Such optical property has been widely applied in the research of reflective LC displays [2], dye lasers [3], etc.…”

Cellulose Nanocrystals as a Sustainable Raw Material: Cytotoxicity and Applications on Healthcare Technology

“…It is noteworthy that chiral molecules (which have no plane of symmetry, i.e., differ from their respective specular images) are packaged to minimize unfavorable steric interactions and maximize attractive dipole interactions . Thus, there is the formation of an optically active macrostructure, the director () of which follows a helical structure, where each nematic layer exhibits a local orientational order along a preferential direction .…”

Light polarization states of a cholesteric liquid crystal probed with optical ellipsometry

“…When the Ch-LC is cooled down, the springs elongate and the sample reflects longer wavelengths (bathochromic shift). On the other hand, when the temperature increases, the springs are compressed and the reflected wavelengths are shorter (hypsochromic shift) [4,5]. Furthermore, these materials feature sufficient optical stability for many applications [6][7][8][9].…”

“…The well-established dissymmetry factor (g) has been used to characterize the reflected or transmitted circular light polarization state of Ch-LC when circular polarized sources are used [3][4][5]12,[18][19][20][21][22][23][24]. Alternative methods have been applied considering the emission ellipsometry technique in the Stokes theory scope for electromagnetic field [25][26][27][28][29].…”