Microdielectrometric monitoring of film preparation process with oriented domains for hydroxypropyl cellulose cast from isotropic aqueous solution under the sinusoidal electric field with large amplitude

Abstract

Microdielectrometry was applied to macroscopically anisotropic media. The distribution and effective portion of the electrostatic energy density, w ₁₄ and J ₁₄, respectively, were calculated, considering the additive contributions of four pairs of microelectrodes. The electric field lines were calculated numerically and investigated experimentally with polarised optical microscopy using thin layers of a nematic liquid crystal with a positive dielectric anisotropy. The applicability of microdielectrometry was investigated using the nematic liquid crystal. Microdielectrometric monitoring was also performed during the preparation process for a solid film with oriented domains with long axes perpendicular to the electric filed cast from an isotropic aqueous solution of hydroxypropyl cellulose under the sinusoidal electric field with large amplitude of 2.0 kV mm⁻¹ and frequency of 10⁵ Hz. In the logarithmic relation between the dielectric constant and loss factor divided by J ₁₄, the two dielectric parameters measured for different film thicknesses at 2.0 kV mm⁻¹ were superposed on a single curve. The curve for the electrically oriented domains was considrably different from that for a randomly oriented polydomain texture found under the electric field with small amplitude of 0.05 kV mm⁻¹ and the same frequency.

Keywords:

• microdielectrometry
• hydroxypropyl cellulose
• cast films
• electrical orientation

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.