Wendy A. Sears, W. M. Sears, C. D. Mackinnon
2008
Citations
0
Influential Citations
9
Citations
Journal
Synthetic Metals
Abstract
Abstract A number of terthiophene derivatives have been synthesized by standard chemical procedures in order to measure the electrical properties of their micro-crystalline powders by impedance spectroscopy, in this case the complex admittance versus frequency. The compounds studied were T 3 , BrT 3 , Br 2 T 3 , T 3 NO 2 , BrT 3 NO 2 , IT 3 NO 2 , and Br-terminated polythiophene. The substituents were all α-position or α,α′-position terminations. The sample powders were placed between a co-axial tube capacitor arrangement and connected to a standard impedance bridge with a frequency range of 20 Hz to 1 MHz. The conductivity showed a simple power law dependence on the frequency with the exponent giving a good indication of the change in conjugation length due to the substituted end group. The push–pull nature of BrT 3 NO 2 and IT 3 NO 2 were clearly seen by the enhancement of both conductivity and susceptibility. The polythiophene sample was significantly more conducting and had a much higher susceptibility. It was observed to undergo a color change, from red to silver, when subjected to shear stress. This was accompanied by an increased conductivity most likely due to an enhancement of π-bond stacking between molecules. The technique presented is a useful and quick way to analyze the potential of new organic semiconductors.