TY - CHAP
T1 - Liquid crystals doped with ionic surfactants for electrically induced anchoring transitions
AU - Krakhalev, Mikhail
AU - Sutormin, Vitaly
AU - Prishchepa, Oxana
AU - Gardymova, Anna
AU - Shabanov, Alexander
AU - Lee, Wei
AU - Zyryanov, Victor
N1 - Publisher Copyright:
© 2021 Walter de Gruyter GmbH, Berlin/Boston.
PY - 2021/1/1
Y1 - 2021/1/1
N2 - Two conceptually different approaches can be used to operate liquid crystal (LC) materials. One approach is based on numerous variants of the Frederiks effect, which enables the LC reorientation caused by external stimuli without a change of boundary conditions. All modern optoelectronic LC devices function on the basis of this effect. The other exploits the anchoring transitions through the modification of the surface anchoring strength with a change in the tilt and (or) azimuthal anchoring angle(s) under the external influence (temperature, irradiation, electric field, and so on). This chapter provides an overview of a novel method to control LC materials by electrically induced anchoring transitions. The key element entailed in our method is an ionic surfactant dissolved in LC. The surfactant is adsorbed partially on the LC cell substrate, thus specifying certain boundary conditions. Its concentration at the interface varied under the action of DC electric field resulting in the modification of the surface anchoring. Following this, changing boundary conditions makes the whole bulk of LC reoriented into a different state. The modification of boundary conditions can be realized in both the normal and inverse modes, depending on the content of the ionic surfactant in LC. This ionic-surfactant operation (ISO) method is applicable to both polymer- dispersed LC (PDLC) films and nematic and cholesteric LC layers. Dynamical parameters of the electro-optical response of various LC structures are considered. Response times of the ISO optical cells of twisted -nematic layers are decreased to tens or hundreds of milliseconds at some volts of applied electric voltage. The implementation of the ISO method into operating PDLC devices allows observations of the novel bistability effects in cholesteric droplets. The most impressive feature of the ISO method is the possibility to reorient LC with dielectric anisotropy Ac of any sign and value, including Ac = 0.
AB - Two conceptually different approaches can be used to operate liquid crystal (LC) materials. One approach is based on numerous variants of the Frederiks effect, which enables the LC reorientation caused by external stimuli without a change of boundary conditions. All modern optoelectronic LC devices function on the basis of this effect. The other exploits the anchoring transitions through the modification of the surface anchoring strength with a change in the tilt and (or) azimuthal anchoring angle(s) under the external influence (temperature, irradiation, electric field, and so on). This chapter provides an overview of a novel method to control LC materials by electrically induced anchoring transitions. The key element entailed in our method is an ionic surfactant dissolved in LC. The surfactant is adsorbed partially on the LC cell substrate, thus specifying certain boundary conditions. Its concentration at the interface varied under the action of DC electric field resulting in the modification of the surface anchoring. Following this, changing boundary conditions makes the whole bulk of LC reoriented into a different state. The modification of boundary conditions can be realized in both the normal and inverse modes, depending on the content of the ionic surfactant in LC. This ionic-surfactant operation (ISO) method is applicable to both polymer- dispersed LC (PDLC) films and nematic and cholesteric LC layers. Dynamical parameters of the electro-optical response of various LC structures are considered. Response times of the ISO optical cells of twisted -nematic layers are decreased to tens or hundreds of milliseconds at some volts of applied electric voltage. The implementation of the ISO method into operating PDLC devices allows observations of the novel bistability effects in cholesteric droplets. The most impressive feature of the ISO method is the possibility to reorient LC with dielectric anisotropy Ac of any sign and value, including Ac = 0.
UR - http://www.scopus.com/inward/record.url?scp=85129343077&partnerID=8YFLogxK
U2 - 10.1515/9783110584370-007
DO - 10.1515/9783110584370-007
M3 - Chapter
AN - SCOPUS:85129343077
SN - 9783110583038
SP - 279
EP - 330
BT - Unconventional Liquid Crystals and their Applications
PB - de Gruyter
ER -