Akademik Veri Yönetim Sistemi
Joint Science Congress of Materials and Polymers (ISCMP), Ohrid, Makedonya, 25 - 28 Ağustos 2017, ss.7
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.