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Two ferroelectric phases of a columnar dibenzopyrene

 

作者: Harald Bock,   Wolfgang Helfrich,  

 

期刊: Liquid Crystals  (Taylor Available online 1995)
卷期: Volume 18, issue 3  

页码: 387-399

 

ISSN:0267-8292

 

年代: 1995

 

DOI:10.1080/02678299508036636

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

The ferroelectric switching of columnar 1,2,5,6,8,9,12,13-octakis-((S)-2-heptyloxy-propanoyloxy)dibenzo[e,l]pyr-2-heptyloxy-propanoyloxy)dibenzo[e,1]pyrene was studied in detail between 60°C and the clearing point 115°C. The switching angle (optical tilt angle) is ±24.5° up to 10V μm−1and ±37° at higher field strengths. The electric polarization is 60nC cm−2in the low field phase and 180nC cm−2in the high field phase. The switching rate has apparent activation energies that increase with voltage from 3 × 10−19to 10−18J. It varies roughly with a power of the voltage, the exponent increasing with decreasing temperature from 2 to 5. At equal voltages, switching is faster in the low field than in the high field phase. We tentatively infer the structures of the two columnar lattices from the ratio of polarizations and other data. From the switching angles, we calculate a tilt angle of 44° for the aromatic cores of the disc-like molecules stacked in the columns. Finally, we point out possible advantages of ferroelectric columnar liquid crystals over their smectic counterparts in electro-optical displays.

 

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