Temperature and Frequency Effects on the Dielectric Properties of the Nematic Liquid Crystal 8CB

1. Temperature and Frequency Effects on the Dielectric Properties of the Nematic Liquid Crystal 8CB By Dr. Chandra Prayaga Ross Dickenson Josh Barbee

2. Overview • Liquid crystals defined • Applications of liquid crystals • UWF Department of Physics research in liquid crystals • Results

3. Liquid Crystals • Materials that have intermediate states between the solid and the liquid phases

4. Applications • Display Technology • Laptop Computers • Digital Watches • Aquarium Thermometers • Waveguide • Optical Switch

5. UWF Physics LC Research • Optical Properties • Thin Films • Microscopy • Electrical: changes in dielectric properties with frequency and temperature

6. RC - Circuit

7. CapacitorConstruction

8. Temperature Control

9. Experimental Apparatus

10. Data Collection Cycle Set Temperature Select Frequencies Record Phase Angle from Lock-In Amplifier Φ = F (freq, Temp) Increase Temperature and Repeat

11. Graph of Data

12. Our Findings • Combinations of Temperature and Frequency Contribute to Phase Angle • Increasing Temperature at any frequency results in a lower phase angle • At low frequency, room temperature, 8CB behaves like a normal dielectric • 8CB’s behavior charges dramatically at transition temperature and medium frequencies

13. Future Efforts • Refine temperature control • Gather more low frequency data in the region of 26deg • Apply a magnetic field and determine upper and lower bounds on the dielectric constant due to alignment of molecules