Concentration dependences of dielectric properties at 10⁵ Hz and 10⁶ Hz for aqueous solutions of hydroxypropyl cellulose

Abstract

The concentration dependences of dielectric properties measured at 10⁵ Hz and 10⁶ Hz are reported for aqueous solutions of hydroxypropyl cellulose. Phase behaviour of the solutions was also observed with a polarizing optical microscope. For solutions with concentrations well above 40 wt %, polydomain textures, including the banded texture, were observed after a prehistory of deformation. No significant discontinuous changes in the dielectric constant, ε_r′, and loss factor, ε_r″, were found at the concentrations around the onset of the isotropic–cholesteric phase transition and in the biphasic region. In contrast, the steeper changes in ε_r′ and ε_r″ were found at the critical concentration for the fully developed cholesteric phase transition with the polydomain textures.

Acknowledgments

This work was partially supported by a Grant‐in‐Aid for Scientific Research from the Japan Society for the Promotion of Science. We are also grateful to Dr. Shimura (TOSOH Analysis and Research Centre Co.) for the dielectric measurements of the solid films.