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Dielectric constants of polymeric materials

  1. Mar 31, 2009 #1
    I have done a series of tests on the dielectric constant of polymeric materials using Impedance measurements in a four electrode configuration.

    When varying the thickness of my polymeric materials, the dielectric constant remains relatively "constant".

    When the thickness of the material is "quite" thin, the dielectric constant jumps from 150 to 750. It is also believed that microchannels exist within the polymeric materials. The polymeric materials also absorb a small amount of whatever solvent the impedance measurements are performed in.

    The polymeric materials contain ionic liquids which from my limited understanding are rather polarizable, despite dielectric dispersion curve studies suggesting that ionic liquid dielectric constants are between 10-12. (Z. Phys. Chem. 2006, 1395-1405, 220, H. Weingartner, The Static Dielectric Constant of Ionic Liquids).

    I am assuming that the ionic liquids contained within the polymeric layer form a series of molecular parrallel plate capacitors.

    Assuming that microchannels exist, I assume that if my micro-channels reached from one side of the polymeric material to the other, (i.e. the polymeric layer had a micro-hole) I would have a leaky capacitor and the resultant Impedance spectra would look more like a resistor, as opposed to giving a larger capacitance (aka more parrallel plates).

    My question to the physics experts:

    Why do I get a larger capacitance for an "ultra thin" layer?
  2. jcsd
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