Dispersion conductivity

Note 6 Electric conductance of a nonconducting polymer can be achieved by dispersing conducting particles (e.g., metal, carbon black) in the polymer. The resulting materials are referred to as conducting polymer composites or solid polymer-electrolyte composites. 

Itoh E, Suzuki 1, Miyairi K (2005) Field emission from carbon-nanotube-dispersed conducting polymer thin film and its application to photovoltaic devices. Jpn J Appl Phys 44 636... 

Dielectric elements that are based on nanostructures are of recent interest for the scaling-down of DRAMs (dynamic random access memories) [11.2]. The need to reduce capacitance requires materials with larger dielectric permittivity. One method to achieve this is to disperse conductive particles in a dielectric matrix by using nanoparticles, the dissipation factor is kept low. 

It was not until 1984 and 1985 that we succeeded in comminuting polypyrrol and polyaniline in the melt by means of ultrasound and dispersing them in special polymer blends. Only two years later we were able to report to the world conference on Organic Metals in Kyoto (Japan) that dispersed conductive polymers displayed a conductivity breakthrough at a concentration of less than ten percent by volume in a thermoplastic polymer matrix—for example a polyvinylchloride (PVC), polyester or polyurethane—and could be processed in the form of such blends. 

Arjsiriwat S, Tanticharoen M, Kirtikara Aoki K et al. Metal-dispersed conducting polymer-coated electrode used for oxidase based biosensor. Electrochemistry Communications 2000 2 441-444. 

X. Li, Y. Zhao, T. Zhuang, G. Wang, and Q. Gu, Self-dispersible conducting polyanihne nanofibres synthesized in the presence of P-cyclodextrin, Colloids and Surfaces A Physicochem. Eng. Aspects, 295,146-151 (2007). 

A. Maity and M. Biswas. Alumina-based water-dispersible conducting nanocomposites of polypyrrole and polypyrrole with poly(A-vinylcarbaz-... 

Resistors Si3N4 matrix with particulates of TiB2, TiC, TiN, or SiC as the dispersed conducting phase... 

At that time, it was rather unclear how and at which concentration a dispersed conductive polymer would conduct after being dispersed in a (polymeric) matrix. With our first patent application [13], we... 

The thermopower measurements themselves show that dispersed conductive polymers have essentially the same thermopower behavior as metals it is small (semiconductors show a high S), and decreases practically linearly with decreasing temperature [18]. These properties were known from our previous measurements [19], which showed the linear temperature dependance for a range of 100 K. These results lead us to the assumption that the primary transport mechanism is metallic, but obviously influenced by a barrier mechanism. To overcome the barrier, a temperature-activated transport process had to be active as well. 

The ability to disperse conducting polymers into insulating hosts such as poly(3-octylthiophene) in polyethylene [217] and PAN-CSA in polymethylmethacrylate [218], or nylon [219], and achieve percolation at less than 1%, increases opportunities for applicatirms. 

Mamunya, E.P., Davidenko, V.V, and Lebedev, E.V. (1995) Percolation conductivity of polymer composites filled with dispersed conductive filler. Polym. Compos., 16, 319-324. 

When the OMF approach is used to fit experimental data, a fatal flaw appears, one that invalidates any conclusions based on such fitting results. For good data, aU CMF fits yield closely the same estimates of % and Pic, independent of the inunit-tance level for the data. This is not the case, however, for OMF fits. They lead to inconsistent results such that fits of the data in M(co) or M"((o) form yield characteristically large values of Pw, usually falling in the range 0.45 < Pio 0.55 for midrange temperatures and concentrations, while fits of the same data in yield values close to 1/3. As mentioned earlier, since has no effect on must yield the same estimates, and OMF and CMF fits are then equivalent. A table of such comparisons and further discussion of OMF problems appear in Macdonald [2004] and make it evident that the OMF treatment of d as an intrinsic part of the K1 dispersive conductive-system model is incorrect. 

Analysis of Dispersed, Conducting-System Frequency-Response Data, J. Non-Cry St. Solids 197, 83-110. 

Melt mixing has been also used to disperse conductive polymers in SBS rubber. Polyaniline doped with dodecylbenzenosulfonic acid was mixed with SBS rubber in a Brabender mixer [119]. A conductivity of 2 S cm was achieved with a loading of 50% of the conductive polymer. According to the authors, this blend could be extruded. However, no supplementary data supporting this conclusion were provided. 

---