A Novel Method for the Measurement of the Nematic Liquid Crystal Twist Elastic Constant

A simple method to measure the twist elastic constant of a nematic liquid crystal

“…Raynes et al proposed another technique using a wedge LC cell filled with a chiral dopant. [15,16] Because of the thickness gradient, the LC directors experience from an untwisted state to a 180°twisted state. Through fitting the threshold voltage at the disclination line, K 22 can be obtained.…”

“…For K 11 and K 33 , a common measurement technique has been established. [10,11] But for K 22 , even though several methods have been proposed, [12][13][14][15][16][17][18][19][20][21] each approach has its own merits and demerits.…”

Experimental Determination of Elastic and Viscous Parameters of Liquid Crystals

“…That is why there are very few materials for which all three elastic constants have been determined with sufficient accuracy, and attempts to improve experimental methods can be found in recent publications [18,29]. It is worthwhile to point out that due to the reasons mentioned above measurements of K 22 are performed with essentially higher errors (more than 10%) than those of K 11 and K 33 .…”

Investigations of twist elastic constant K22 of new nematic liquid crystal materials using threshold IPS method

“…9 and 11. The values of twist elastic con− stants for E7 material are between 5 and 9 pN [8,9,11,14]. These values give about 55% uncertainty of the calculated values.…”

“…From a few known measurement techniques [6][7][8][9][10][11][12][13][14], we have chosen the most widely used method of determining twist elastic constant which could be integrated easily with temperature chambers and could be used for all nematic materials in regard to dielectric anisotropy. Comparison of all methods is shown in Table 1.…”