AN ELECTRON-SPIN-RESONANCE STUDY OF POLYANILINE AND ITS DERIVATIVES -POLYMER INTERACTIONS WITH MOISTURE

The electronic behavior of polyaniline is sensitively dependent on moi sture. For example, pumping under vacuum leads to an order of magnitud e smaller conductivity, increased dielectric constant, and increased C urie susceptibility. An understanding of the mechanism of conductivity enhancement and changes in the other properties due to absorbed moist ure thus requires better insight into the nature of the absorbed water . An electron spin resonance study has therefore been undertaken to fi nd the various absorption/adsorption sites for water molecules. A numb er of experiments has been performed which lead us to propose a ''vari able-size metallic island'' model. That is, protonated and highly orde red regions (metallic islands) are separated from unprotonated and amo rphous regions by a less ordered region, whose width depends on the am ount of moisture present in the sample. The water in the boundary regi on reduces its width by introducing order and thereby transforming par tly localized polarons into bipolarons. The conductivity enhancement i s argued to be due to increased size of the metallic islands in the pr esence of moisture.