Acid doping

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]. 

HPA-composite catalysts have also been studied for ORR.166 A conducting polymer and HPA were combined to form the 12-phosphormolibdic acid-doped polyaniline-V202 composite. The composite showed improved activity over the conducting polymer alone in a weak acid solution. 

Wainright, J. S., Wang, J.-T., Savinell, R. F. and Lift, M. 1995. Acid-doped poly-benimidazoles A new polymer electrolyte. Journal of the Electrochemical Society 142 L121-L123. 

One of the problems associated with the use of heterocycles is that the intrinsic concentration of protonic charge carriers can only be moderately increased through acid doping (also see Section 4.3). This is particularly the case when the dynamics within the hydrogen-bonded domain is highly constrained through immobilization (especially in fully polymeric systems), which is probably the direct consequence of a reduced dielectric constant. This also leads to a further increase of the Haven ratio... 

It is important to realize that these oligomers have similarly low vapor pressures as ionic liquids. To illustrate the effect of extrinsic charge carrier formation, the evolution of proton conductivity with triflic acid doping is shown for the oligomeric system Imi-2 in Figure For such systems, the mobility of... 

Figure 24. Proton conductivity of Imi-2 (two imidazoles spaced by two ethylene oxide (EO) units), as a function of triflic acid doping.237 Note that the conductivity has a tendency to level off at high acid concentration (see insert).

Hanson, D. R., and A. R. Ravishankara, Investigation of the Reactive and Nonreactive Processes Involving CIONOj and HCI on Water and Nitric Acid Doped Ice, J. Phys. Chem., 96, 2682-2691 (1992b). 

LB films prepared from poly(thiophene-3-acetic acid)-stearylamine and from sulfonatedpolyaniline-stearylaminepolyion complexes, transferred to substrates, and doped by acid FTIR, X-ray diffraction, and conductivity measurements Lateral d.c. conductivities of acid-doped films as high as 0.05 S cm"1 were obtained 768, 769... 

Fig. 10.1. Analysis of die fitness landscape for a basic amino acid dope (30% Arg, 30% Lys, 40% His), (a) Nonlinear projection of die seven-dimensional solution space onto two dimensions by a self-organizing map (SOM) [14]. The seven dimensions are (Tl, Cl, Al, T2, C2, A2, C3), encoding fractions of nucleoddes for each NN(G/C) codon position. The mean squared error between die computed and desired amino acid concentrations are indicated by shades of grey here and by color in die copy of diis figure on die CD diat accompanies diis book.

Fig. 10.1 (Continued), (b) Distribution of local optima in solution space for a basic amino acid dope (30% Arg, 30% Lys, 40% His). Due to die structure of die genetic code, a perfect soludon of fracdons of nucleotides for die given example does not exist. Instead, several islands of different suboptimal solutions are found. Seven local optima, marked by different colors (see die color version on die CD diat accompanies diis book), can be identified. Note diat die SOM uses toroidal boundaries, i.e., die left-most and right-most points lie close togedier, as do die top and bottom points.

Fig. 10.1 (Continued), (c) Distribution of solutions within each local optimum for a basic amino acid dope (30% Arg, 30% Lys, 40% His). Each cluster consists of many different solutions, which are overlaid in die profile plots, revealing some trends. Each cluster emphasizes a different typical profile of solutions - and clusters 2 and 5 are especially different from die odier clusters. Comparing die mean values of each nucleodde between die clusters shows large differences, especially for die nucleotide fractions A1 and C3. The standard deviation for each nucleotide is 10%.

PANI is unique in that its most oxidized state, the pernigraniline form (which can be accessed reversibly), is not conducting. In fact, it is the intermediately oxidized emeraldine base that exhibits the highest electrical conductivity. Protonic Acid Doping is the most general means by which to obtain this partially pro-tonated form of PANI [301]. Exposure of the emeraldine salt to alkali solutions reverses this process and brings a return to the insulating state. 

Clear quantitative descriptions of the transport in poorly defined material systems such as acid-doped PANI or mats and ropes of nanotubes are difficult to develop. Even more problematic is the description of a composite of the two. Nevertheless we do believe that there are some conclusions that can be drawn from consideration of the data. A large amount of work has gone into understanding the transport in heterogeneous systems such as conducting polymers and nanotube mats [25, 27-31]. However, that work has focused on understanding each separately rather than as a combined composite material. Interestingly, when com-... 

Chiang J, MacDiarmid AG (1986) Polyaniline protonic acid doping of the emeraldine form to the metallic regime. Synth Met 13 193-205... 

Handon DR, Ravishankara AR (1992) Investigation of the reactive and nonreactive processes involving nitryl hypochlorite and hydrogen chloride on water and nitric acid doped ice. J Phys Chem 96 2682-2691... 

FIG. 11.18 Conductivity of emeraldine base as a function of pH of the HCl dopant solution as it undergoes protonic acid doping ( ) and ( ) represent two independent series of experiments. From MacDiarmid, 2001. Courtesy John Wiley and Sons, Inc. 

FIG. 11.19 Oxidative doping (p-doping) of leuco-emeraldine base and protonic acid doping of emeraldine base, leading to the same final product, emeraldine salt. Reproduced from Fig. 34.3 in Mark (1996). Courtesy Springer Verlag. 

Litwinienko et al. (1997) reported that non-isothermal (conventional) DSC and P-DSC analyses can evaluate antioxidant activity in linolenic (Ci8 3) acid doped with phenolic antioxidants. Activation energies were inferred by applying the Ozawa-Flynn-Wall analytical method. Results showed that increasing BHT loading from 0.3 to 4.0mM increased the activation energy of oxidation from 73.0 to 97.8kJ/mol. 

Rhenium(I) tricarbonyl-2,2 -bipyridine moieties were used to cap both ends of a poly fluorine, yielding Re-capped Re(bpy)(CO)3(py)-X-(py)(CO)3(bpy)Re 2+ polymers, where X = polyfluorene [51, 52], The polymers with and without the Re caps were spin-coated from their solutions in CH2C12 onto an ITO surface previously modified with a layer of poly(styrene sulfonic acid), doped with poly(ethylenedioxythiophene). The LED (light-emitting device) was then topped with a layer of Ca/Al. The photoluminescence (PL) and electroluminescence seen were consistent with the presence of [Re(bpy)(CO)3(py)]+ [158],... 

Nanotubes using lignosulfonic acid-doped polyaniline were prepared by Vis-wanathan [2]. 

Savadogo, O. and Xing, B., Hydrogen/oxygen polymer electrolyte membrane fuel cell (PEMFC) based on acid-doped polybenzimidazole (PBI), J. New Mater. Electrochem. Syst., 3, 345, 2000. 

Wainright, J.S. et ah. Acid-doped polybenzimidazoles a new polymer electrolyte, J. 

Samms, S.R., Wasmus, S., and Savinell, R.F., Thermal stability of proton conducting acid doped polybenzimidazole in simulated fuel cell environments, J. Electrochem. Soc., 143, 1225, 1996. 

Hasiotis, C. et al.. Development and characterization of acid-doped polybenzimid-azole/sulfonated polysulfone blend polymer electrolytes for fuel cells, J. Electrochem. Soc., 148, A513, 2001. 

Li, Q., Hjuler, H.A., and Bjerrum, N.J., Phosphoric acid doped polybenzimidazole membranes physiochemical characterization and fuel cell applications, J. Appl. Electrochem., 31, 773, 2001. 

Li, Q., Jensen, J., He, R., Bjerrum, N. (2004). New polymer electrolyte membranes based on acid doped PBI for fuel cells operating above 100°C. In "Hydrogen Power - Theoretical and Engineering Solutions, Proc. Hypothesis V, Porto Conte 2003" (Marini, M., Spazzafumo, G., eds.), pp. 685-696. Servizi Grafici Editoriali, Padova. 

As mentioned in the introduction, the electrical conductivity upon doping is one of the most important physical properties of conjugated polymers. The conductivity ranges from lOOOOOS/cm for iodine-doped polyacetylene [41], 1000 S/cm for doped and stretched polypyrrole [42], to 500 S/cm for doped PPP [43], 150 S/cm for hydrochloric acid doped and stretched polyaniline [44], and 100 S/cm for sulfuric acid doped PPV [45] to 50 S/cm for iodine-doped poly thiophene [46]. The above listed conductivities refer to the unsubstituted polymers other substitution patterns can lead to different film morphologies and thus to a different electrical conductivity for the same class of conjugated polymer in the doped state. 

Hydrochloric acid as well as camphor sulfonic acid doped polyaniline prepared in chloroform often have [59] log a proportional to T as expected for quasi-one-dimensional variable range hopping, Equations (3) and (4). Generally, the higher conductivity samples have a weaker temperature dependence at low temperatures (Tq 700-1000 K for T<80 K), and lower conductivity samples a stronger temperature dependence (To 4000 K). The smaller Tq for the more highly conducting samples has been associated with weaker localization due to improved intrachain and interchain order. 

Figure 8 Thickness dependence of total shielding efficiency (SET) of highly conducting polymers (A) stretched heavily iodine doped Tsukamoto polyacetylene, (B) camphor sulfonic acid doped polyaniline cast from m-cresol solvent, (C) PFg doped polypyrrole.

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