Effect of polymer relaxation on dielectric spectroscopic study of polymer-ferroelectric liquid crystal composites

Polymethylmethacrylate (PMMA) and ferroelectric liquid crystal (P-FLC) composite films (~ 4 μm) with varying proportions of ferroelectric liquid crystal have been prepared and the dielectric response of the composite films as a function of wide frequency (100 Hz-10 MHz) and temperature (127-40 °C) have been analyzed. The dielectric spectra of such composite systems are considerably modified compared to those of the corresponding pure LC or PMMA materials. The observed paraelectric to ferroelectric transition temperature of the composites is found to be lower (~ 85 °C) compared to that of the pure LC system (~ 98 °C), which makes these composites technologically more significant. The P-FLC composites also exhibit higher relaxation frequency and smaller dielectric strength for the Goldstone mode compared to those of the corresponding pure FLC. Depending on the percentage of the constitute materials, the molecular dynamics of the composite materials changes. Dielectric contributions of both liquid crystal and PMMA matrix forming the composites have been analyzed on the basis of Havriliak and Negami function.