Electrical conduction in composites of a TCNQ anion‐radical salt in a polymer matrix

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Abstract
The conduction behavior of composites of the anion‐radical salt NaTCNQ (sodium 7,7,8,8‐tetracyanoquinodimethanide) in poly(vinyl chloride) plasticized by polyurethane has been studied. TCNQ salt‐polymer composites that have good moldability and flexibility are characterized by molecular or granular dispersion of the TCNQ salt in a polar polymer matrix. The conduction mode changes from one due to molecularly dispersed sites (CMDS) to one due to granularly dispersed sites (CGDS) with increasing NaTCNQ content. In the CMDS region, the predominant conduction is ionic; TCNQ anion‐radicals migrate toward the anode under a dc biasing voltage and a high‐resistivity layer is formed near the cathode. The fixation of TCNQ salt at sites in the polymer matrix is believed to be important for the stabilization of electronic conduction under a dc electric field. In the CGDS region, the conduction is electronic and the current‐voltage characteristics of the composite are nonohmic, which indicates that carrier generation depends on the Poole‐Frenkel effect.