Publication Title

Physical Review E

Publication Date

2-15-2005

Document Type

Article

DOI

10.1103/PhysRevE.71.021709

Keywords

ferroelectric liquid-crystals, photochemical control, achiral molecules, polarization, phase, dye, photoisomerization, isomerization, behavior, films

Disciplines

Physics

Abstract

We have studied the optical and electrical properties of two bent-core substances with an azo linkage in their cores. Pump-probe laser studies, direct textural observations, and spectrophotometric recordings show an initial decrease of light transmission, which at larger light intensities (similar to 1 mW/mm(2)) is followed by a bleaching. Simultaneously the electrical properties (electric conductivity, antiferroelectric polarization, switching threshold, and switching time) decreased monotonically with increasing light intensities. The monotonic decrease of electrical properties indicates that the darkening and bleaching have the same origin, namely, the photochemical isomerization of the azo linkage from the trans to the cis isomer. The material with cis isomer has a lower clearing point and phase separates from the trans-rich domains. Initially the size of the separated isotropic domains is below the visible range, which causes increased scattering. As the size of the isotropic domains increase the scattering disappears and the transmittance becomes the average of the transmittances in the polar tilted smectic and isotropic phases.

Comments

Copyright 2005 American Physical Society. Available on publisher's site at http://dx.doi.org/10.1103/PhysRevE.71.021709


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