Study of electrical properties of polymeric materials using electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy (EIS) has been used to determine the water absorption characteristics of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyaromatic amide (Aramid), and amine-quinone polyurethane (AQ) free-standing polymer films. A method for calculating percent moisture uptake is presented based on capacitance measurements via EIS, which requires initial or "dry" capacitance values, C-0. Three different methods for obtaining C-0 values were described and employed, but the most reliable values were obtained via EIS measurement using Hg contacts. C-0 values obtained by this method resulted in calculated water uptake values nearly identical to those obtained by measured weight gain. Lower capacitance values were observed for films immersed in distilled water compared to 0.1M NaCl, which indicates that water uptake is greater in NaCl than in pure water. The four polymers examined in this study can be listed in order of decreasing resistance to moisture absorption as AQ > PET > PEN > Aramid. (C) 1998 John Wiley & Sons, Inc.