The Effect Of Ionic Charge Carriers In 2-Hydroxyethyl Cellulose Solid Biopolymer Electrolytes Doped Glycolic Acid Via FTIR-Deconvolution Technique

Abstract

The Fourier transform infrared (FTIR) spectrum of each 2-hydroxyethyl cellulose (2HEC) doped with glycolic acid (GA) solid biopolymer electrolytes (SBE) sample has been deconvoluted in the wavenumber region between 1390 and 1490 cm-1 in order to predict the percentage of free and contact ions in the samples. Through solution casting method, 2HEC was complexed with different composition of GA and sample with 40 wt. % GA achieved the highest ionic conductivity at room temperature of 4.01x10-4 S cm-1, two magnitude orders higher relative to the parent host polymer. The FTIR of carboxyl stretching mode is deconvoluted, representing bands of free ions, contact ion pairs and ion aggregates to obtain an insight on ion associations. The results show that the number of free ions increases and attain maximum at 40 wt. % GA. The correspondence between free ions, contact ion pair, ion aggregates and conductivity is obvious. The increase in ion dissociation improves conductivity, while the formation of contact ion pair and ion aggregates reduces conductivity. From Transference Number Measurement (TNM), the calculated ionic species of the 2HEC-GA complexed system is confirmed predominant cationic.