TY - JOUR
T1 - A Fluid Liquid-Crystal Material with Highly Polar Order
AU - Nishikawa, Hiroya
AU - Shiroshita, Kazuya
AU - Higuchi, Hiroki
AU - Okumura, Yasushi
AU - Haseba, Yasuhiro
AU - Yamamoto, Shin Ichi
AU - Sago, Koki
AU - Kikuchi, Hirotsugu
N1 - Publisher Copyright:
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/11/20
Y1 - 2017/11/20
N2 - An anomalously large dielectric permittivity of ≈104 is found in the mesophase temperature range (MP phase) wherein high fluidity is observed for a liquid-crystal compound having a 1,3-dioxane unit in the mesogenic core (DIO). In this temperature range, no sharp X-ray diffraction peak is observed at both small and wide Bragg angles, similar to that for a nematic phase; however, an inhomogeneous sandy texture or broken Schlieren one is observed via polarizing optical microscopy, unlike that for a conventional nematic phase. DIO exhibits polarization switching with a large polarization value, i.e., P = 4.4 µC cm−2, and a parallelogram-shaped polarization–electric field hysteresis loop in the MP phase. The inhomogeneously aligned DIO in the absence of an electric field adopts a uniform orientation along an applied electric field when field-induced polarization switching occurs. Furthermore, sufficiently larger second-harmonic generation is observed for DIO in the MP phase. Second-harmonic-generation interferometry clearly shows that the sense of polarization is inverted when the +/− sign of the applied electric field in MP is reversed. These results suggest that a unidirectional, ferroelectric-like parallel polar arrangement of the molecules is generated along the director in the MP phase.
AB - An anomalously large dielectric permittivity of ≈104 is found in the mesophase temperature range (MP phase) wherein high fluidity is observed for a liquid-crystal compound having a 1,3-dioxane unit in the mesogenic core (DIO). In this temperature range, no sharp X-ray diffraction peak is observed at both small and wide Bragg angles, similar to that for a nematic phase; however, an inhomogeneous sandy texture or broken Schlieren one is observed via polarizing optical microscopy, unlike that for a conventional nematic phase. DIO exhibits polarization switching with a large polarization value, i.e., P = 4.4 µC cm−2, and a parallelogram-shaped polarization–electric field hysteresis loop in the MP phase. The inhomogeneously aligned DIO in the absence of an electric field adopts a uniform orientation along an applied electric field when field-induced polarization switching occurs. Furthermore, sufficiently larger second-harmonic generation is observed for DIO in the MP phase. Second-harmonic-generation interferometry clearly shows that the sense of polarization is inverted when the +/− sign of the applied electric field in MP is reversed. These results suggest that a unidirectional, ferroelectric-like parallel polar arrangement of the molecules is generated along the director in the MP phase.
KW - dielectric anisotropy
KW - ferroelectric-like polarization
KW - highly polar order
KW - liquid crystals
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U2 - 10.1002/adma.201702354
DO - 10.1002/adma.201702354
M3 - Article
C2 - 29023971
AN - SCOPUS:85031099669
SN - 0935-9648
VL - 29
JO - Advanced Materials
JF - Advanced Materials
IS - 43
M1 - 1702354
ER -