Helical Twisting Power change-induced pitch modulation of cholesteric LC

Cholesteric LC (CLC), due to the presence of macroscopic helix, give rise to finger print texture acting like a diffraction grating with a periodicity in the range of a few to tens of micrometers. The pitch of the helix, responsible to the grating can be easily tuned by external fields such as temperature, electric field, optical field etc. In the present study, a CLC obtained by the addition of small concentration of a chiral dopant to a nematic LC exhibited a right handed helical pitch at ambient temperatures. Upon heating, pitch diverges leading to unwinding of the helix resulting in a compensated nematic phase. On further heating the composite, a left-handed helical superstructure is formed before finally transforming to the isotropic phase. Such tunability of helical pitch and thus the grating spacing is promising in beam steering applications. See Adv. Mater. 2017, 29, 1700676(1-5).

Posted by Geetha Nair