Conducting polymer temperature-dependence

In a numerical solution, we can include temperature dependent density and thermal conductivity. The temperature dependent density can be modeled interpolating throughout a pvT diagram. The temperature dependence of the thermal conductivity is not always available, as is the case for many properties used in modeling. Chapter 2 presents the Tait equation, which can be used to model the pvT behavior of a polymer. 

A conductivity study on PVC-PMMA-LiAsFg-DBP polymer blend electrolyte by S. Rajendran, T. Uma, and T. Mahalingam (Rajendran et al., 2000) revealed the effect of PVC-PMMA blend ratio on ionic conductivity. The temperature dependence of the conductivity of the polymer films obeys the Vogel-Tamman-Fulcher (VTF) relationship. 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

Fig. 1. (a) Comparison of normalised electrical conductivity of individual MWCNTs (Langer 96 [17], Ebbesen [18]) and bundles of MWCNTs (Langer 94 [19], Song [20]). (b) Temperature dependence of resistivity of different forms (ropes and mats) of SWCNTs [21], and chemically doped conducting polymers, PAc (FeClj-doped polyacetylene [22]) and PAni (camphor sulfonic acid-doped polyaniline [2. ]) [24]. 

One more fact, important in practice, lies in that a of the compositions based on heterogeneous blends of polymers obtained by the method 3, depends considerably on mixing temperature Tm. This is bound up with a variation of the polymer viscosity with the temperature on being introduced into the polymer mixture, a filler becomes distributed mostly in the less viscous polymer and, if the viscosity of polymers is almost the same, it is distributed comparatively uniformly and a of the composition decreases. Therefore, the dependence of a of the conducting polymer composite on Tm has a minimum (by a factor of 102 to 104) in the Tm region when the viscosities of the polymer components are close. 

Using Eq. (2.6.18) the temperature dependence of various transport properties of polymers, such as diffusion coefficient D, ionic conductivity a and fluidity (reciprocal viscosity) 1/rj are described, since all these quantities are proportional to p. Except for fluidity, the proportionality constant (pre-exponential factor) also depends, however, on temperature,... 

Bv employing a soluble cationic polymer as the solution electrolyte polymer films can be sterical ly blocked from reducing beyond the formal zero valent form. In the zero-valent form the polymer is an ohmic conductor both in solution and dry. A model has been proposed which describes the conductivity of the polymer and in part accounts for its ohmic nature and semi conductor-1 ike temperature dependence. 

Figure 3 Temperature dependence of ionic conductivity for polymers 1 and 2 in the presence of various lithium salts.

In the presence of lithium salts, the temperature dependence of ionic conductivity for the polymer electrolytes obtained was evaluated. In the presence of LiCF3S03,... 

Figure 12 (a) Temperature dependence of ionic conductivity, (b) VFT plots for polymer/salt hybrids 10. 

Many polymer-salt complexes based on PEO can be obtained as crystalline or amorphous phases depending on the composition, temperature and method of preparation. The crystalline polymer-salt complexes invariably exhibit inferior conductivity to the amorphous complexes above their glass transition temperatures, where segments of the polymer are in rapid motion. This indicates the importance of polymer segmental motion in ion transport. The high conductivity of the amorphous phase is vividly seen in the temperature-dependent conductivity of poly(ethylene oxide) complexes of metal salts. Fig. 5.3, for which a metastable amorphous phase can be prepared and compared with the corresponding crystalline material (Stainer, Hardy, Whitmore and Shriver, 1984). For systems where the amorphous and crystalline polymer-salt coexist, NMR also indicates that ion transport occurs predominantly in the amorphous phase. An early observation by Armand and later confirmed by others was that the... 

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