Investigation of a relationship between Free Volume and Ionic Conductivity of PVdF-co-HFP with Ionic Liquid


Yakut Ş. , Yahşi U., Tav C., Erdemci G., Coşkun B., Deligöz H., ...More

Joint Science Congress of Materials and Polymers (ISCMP), Ohrid, Macedonia, 25 - 28 August 2017, pp.7

  • Publication Type: Conference Paper / Summary Text
  • City: Ohrid
  • Country: Macedonia
  • Page Numbers: pp.7

Abstract

Polymer matrix-ionic liquid (IL) complexes are of growing interest due to viable transport properties

and potential applications in fuel cells and such other ionic devices as polymer electrolytes.

Polymer electrolytes contain local free volumes which are formed by irregular molecular packing

and affect thermal, mechanical, and transport properties of polymers. Their conductivity is

related to the hole fraction as a measure of free volume, calculated from the Simha-Somcynsky

theory. [1] In this work, we purpose to establish a correlation between the hole fraction and ionic

conductivity of polymer-based IL electrolytes. For this aim, polymer electrolytes containing 1,

3, 10, 30% of (weight) amounts of IL (1-etil 3-metil imidazolyum tetrafloroborat) were prepared

by solution casting method. All these electrolytes were based on PVdF-co-HFP. The conductivity

measurements of the samples were run by AC impedance analyzer from 273 K to 373 K temperature

intervals. The hole fraction of the samples was measured by ortho-positronium (o-Ps) lifetime and

intensity using Positron Annihilation Lifetime Spectroscopy (PALS). [2] The changes of nanoscopic

hole free volume and hole fraction were investigated with respect to temperature which had

an increasing effect on them. However the hole fraction increased sharply to about 1% of IL

fraction. It is the fact that the formation of polymer and salt complications which occur between

the fluorine groups in the polymer backbone and Li+ ion in salt retards the ordering of polymer

crystalline and causes the formation of amorphous phases. As the weight ratio was greater than

1%, the hole fraction decreased because of the IL occupation in the holes and then saturated.