Arrhenius behavior conductive polymers

Figure 6.12 shows the results of the proton conductivity of the SPTES polymers and Nafion-117 at 85% relative humidity at different temperatures. In all the cases, an increase of the membrane proton conductivity with increasing temperature is indicated. All the SPTES polymer membranes exhibited higher proton conductivity than Nafion-117 except in the lower temperature region for SPTES-50 polymer where a slight crossover is indicated. The proton conductivities of SPTES polymers have a linear dependence on temperature, thus showing Arrhenius behavior. The activation energy related to the proton conductivities of the SPTES polymers has been reported elsewhere [29]. 

The electrical response observed in conventional polymer is usually interpreted by non-Arrhenius behavior. The temperature dependence of DC conductivity measured from the polymer electrolytes is the hallmark of ionic motion being coupled with the host matrix. The temperature dependence of the conductivity exhibits an apparent activation energy that increases as temperature decreases. This behavior is most commonly described by the empirical VTF equation, which was first developed to describe the viscosity of supercooled liquids. However, there is a different class of polymer electrolyte, discussed and first reported by Angell, suggesting that the ionic conductivity is not coupled to the segmental motion of the polymer chain, that is, in which the ions move independently of the viscous flow. ° Based on this approach, Souza recently reported a new class of DHP (synthesis route discussed above), in which the ion mobility presented an Arrhenius behavior of the conductivity as a function of temperature, suggesting that the ion motion is decoupled from the polymer segmental motion for temperatures above Tg (about... 

The same type of methodology was also used to prepare ferrocene-containing arylidene polyesters 122 in good yields from dicarboxyl ferrocenes and organic diols. These materials were characterized by elemental analysis, IR spectroscopy, viscometry, and WAXS. The polymers were found to be semicrystalline but were soluble in polar organic solvents. Conductivity studies showed an n-type semiconductor behavior (cr = 3 x 10 Scm at room temperature) that followed a one-term Arrhenius-type equation with increasing conductivity over the range 25-220 °G. 

The Arrhenius plot of these polyurethanes is representative of thermoplastics with phase-separated structure (Fig. 6.25).The data for the DC conductivity show a typicd VTFH-type behavior [Eq. (6.24)] (Tuncer et al. 2005), consistent with the coupling of the conductivity mechanism with cooperative segmental motions usually observed in linear polyurethanes and several other thermoplastics. The glass transition temperatures determined by DEA (Tg diei), DSC (TgDsc), and thermally stimulated current (Tg xsc) show very good agreement. In addition, the majority of published works on polymers [e.g., see... 

Morales et al. [323] prepared bionanocomposites of PEA (derived from glycohc acid and 6-aminohexanoic add by in situ polymerization) reinforced with OMMTs. The most dispersed structure was obtained by addition of C25A organoclay. Evaluation of thermal stability and crystallization behavior of these samples showed significant differences between the neat polymer and its nanocomposite with C25A. Isothermal and nonisothermal calorimetric analyses of the polymerization reaction revealed that the kinetics was highly influenced by the presence of the silicate particles. Crystallization of the polymer was observed to occur when the process was isothermally conducted at temperatures lower than 145 °C. In this case, dynamic FTIR spectra and WAXD profiles obtained with synchrotron radiation were essential to study the polymerization kinetics. Clay particles seemed to reduce chain mobility and the Arrhenius preexponential factor. 

The conductivity of P (MEO-7)/MSCN hybrid film was measured at different temperatures ranging from 0 to 80 °C, and the Arrhenius plot for each system is shown in Fig. 8 [8]. The all of these could be drawn as curved line rather than linear. In other words, the ionic conduction mechanism in each system is considered to obey the Williams-Landel-Ferry(WLF) behavior, in which ionic movement is influenced by the segmental motion of the polymers. 

The ionic conductivities of the gel polymer electrolytes made by polymerization of the two monomers, respectively, shown in Figure 11.15, and plasticizing with 1.1 M LiPFg solution in EC/PC/ethyl methyl carbonate (EMC)/ DEC (weight ratio, 30 20 30 20) is up to 5-6 x 10" S/cm at 20°C. As shown in Figure 11.16, the ion conductive behavior does not follow the Arrhenius equation. The distance between the cross-linking points in the polymer network... 

Pure PEO has also been used in an electrolyte for DSSC, by combining this polymer with different amounts of KI and Using Raman spectroscopy the authors showed the formation of polyiodide species in the electrolyte upon addition of different salt and iodine concentrations. The highest ionic conductivity achieved at room temperature was 8.4 x 10" S cm for the electrolyte composition PEOrKI 12 1 0.1. Fourier transform infrared (FTIR) spectroscopy was carried out to show that the K+ ions can coordinate to the ether oxygen in PEO chains and a linear Arrhenius-type behavior was observed. DSSC assembled with this electrolyte presented = 6.1 mA cm , Voc = 0.59 V, fill factor FF = 0.56 and rj = 2.0% under irradiation of 100 mW cm Polymer electrolytes containing different salts, such as quaternary ammonium iodides, or different polymers, such as poly(butylacrylate) and poly(dimethylsiloxane), have also been used in DSSC. 

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