Dielectric relaxation spectroscopy and alignment behavior of a polymer‐dispersed liquid crystal and its component materials

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AbstractThe dielectric properties of a polymer‐dispersed liquid crystal (PDLC), a liquid‐crystal (LC) mixture (BL036), and three polymer matrices of PN314 containing different amounts of BLO36 were determined over a range of frequencies and temperatures and, for the LC and PDLC, over a range of voltages leading to homeotropic alignment of the LC. The overall dielectric relaxation process was a weighted sum of contributions from (1) the primary (δ) process in the LC arising from the motions of the dipoles about the short molecular axis and (2) dipole motions in the polymer matrix. The dielectric spectra were determined as a function of frequency, temperature, and, when appropriate, applied voltage. An equivalent electrical circuit was used as a working model to describe the dielectric behavior of the PDLC in the absence and presence of applied voltages. Agreement between the dielectric data and this model was achieved if a portion of the LC phase at the interface was assumed to be immobile. The director order parameter for the LC component in the PDLC was determined from dielectric measurements as the material was aligned homeotropically in an applied electric field. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1173–1194, 2001