Electron beam irradiation induced changes in liquid-crystal compound 5CB

Abstract

Electron beam irradiation studies on liquid crystal material 5CB have been carried out at a temperature where the compound exists in the isotropic liquid phase. In situ time-resolved spectroscopic characterization was carried out during the irradiation. Three different transients were observed during the 2-μs electron pulse. After about 50 μs, only one transient species was found to be present, which has an absorption peak at 360 nm. Radiolysed sample exhibits a broad absorption at ∼400 nm. The dielectric measurements show that even a low level of irradiation results in a dramatic increase in the component of dielectric permittivity normal to the long axes of the molecules ε⊥′, and a corresponding decrease in the dielectric anisotropy (Δε′=ε∥′−ε⊥′ ). These studies show that 5CB is prone to substantial radiation damage on exposure to the beam of high-energy electrons.

Electron beam irradiation induced transformations in the electro-optical and dielectric properties of a twisted-nematic display material 4′-pentyl-4-cyanobiphenyl (5CB)

“…Electron pulses of 2 µs duration were used. The radiolytic transients were analysed in situ by a kinetic spectrometer assembled at the LINAC set-up and the results are reported elsewhere [16]. The samples were given various amounts of cumulative doses up to ∼20 kGy for investigating their steady-state electro-optical and dielectric parameters.…”