Piezoelectric Characteristics of Polymer Film Oriented under a Strong Magnetic Field

• Published in: Japanese Journal of Applied Physics Vol. 43; no. 9S; p. 6769
• Main Authors: Nakiri, Takuo, Imoto, Kenji, Ishizuka, Masayuki, Okamoto, Satoshi, Date, Munehiro, Uematsu, Yoshiko, Fukada, Eiichi, Tajitsu, Yoshiro
• Format: Journal Article
• Language: English
• Published: 01.09.2004
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.43.6769

The possibility has been indicated that polymers with helical chirality, such as poly-γ-benzyl-L-glutamate (PBLG) and poly-L-lactic acid (PLLA), exhibit a large shear piezoelectric constant. To attempt the realization of a PBLG membrane with a large piezoelectric constant, we fabricated the PBLG membrane oriented by magnetic field force. Concretely, the PBLG membranes were casted from 1,2-dichloroethane solution with various PBLG concentrations under the magnetic field generation equipment incorporating a superconducting magnet. First, the orientation of the chain molecules of the PBLG membranes obtained was observed macroscopically by means of a polarizing microscope (POM). The orientation of the chain molecules of the PBLG membranes was recognized for the case of casting from the PBLG 1,2-dichloroethane solution in the liquid crystal state. Also, from X-ray photograph measurements, it was found that the orientation direction of the chain molecules of PBLG was perpendicular to the magnetic field direction. We then measured the shear piezoelectric constant d 14 of the oriented PBLG membranes. With increasing the strength of the applied magnetic field in the casting process for the film preparation, d 14 * of the PBLG membranes obtained increases. Finally, a large piezoelectric constant of 26 pC/N was found in the PBLG membrane. It is assumed that d 14 * is not saturated even at the magnetic field of 10 T.