Phase Transitions in Smectic Bent-Core Main-Chain Polymer Networks Detected by Dielectric and Ultrasonic Techniques

Abstract

The dielectric and ultrasonic properties of a bent-core main-chain liquid-crystalline polymer network have been investigated. Dielectric measurements on this material showed two maxima in the real and imaginary components of the dielectric permittivity at 365 K and 450 K along with a temperature hysteresis showing the first order nature of the two phase transitions. Longitudinal ultrasonic attenuation and ultrasonic velocity measurements at 10 MHz frequency revealed some anomalies at the phase transition temperatures respect to the dielectric results. Above room temperature, a large ultrasonic attenuation was observed which can be related to the glass transition of this sample. Moreover, the piezoelectric sensitivity of this bent-core main-chain liquid-crystalline polymer network has also been studied.

• Keywords Polymer network
• bent-core
• liquid crystals
• phase transitions
• ultrasonic properties
• dielectric properties

Acknowledgments

We thank Prof. R. Mezzenga for insightful comments and his support to this work.

Funding

This work was supported by the Lithuanian Research Council under project MIP-068/2012.