Secondary dopants

In this derivation, it was assumed that the charge-transfer complex is formed between the p- or n- primary dopant and the gas acts as a secondary dopant. In fact, the interaction of the secondary dopant with any energy state in the matrix is possible that would lead to the same result, as long as the exchanged electron density becomes part of the electron population governed by the Fermi-Dirac statistics. The analytical utility of this relationship has been shown for several inorganic gases (Janata and Josowicz, 2003). 

Other phenolic compounds have also been shown to cause similar changes in conformation and physical properties of PAn/HCSA salts.24-28 Most of these, for example, m-cresol, are highly corrosive and toxic, limiting their desirability for processing and enhancing the electrical conductivity of PAn s. However, we have recently found that the structurally related molecules thymol 2 and carvacrol 3, which are much less toxic than m-cresol, can also function as effective secondary dopants for PAn/(+)-HCSA films and increase the electrical conductivity by up to two orders of magnitude.28... 

PPy doped with protonic acid shows a higher electrical conductivity compared to that doped with organic sulfonic acid (Lee et al., 2014), and a PPy film with electrical conductivity up to 2000 S cm 1 was prepared (Qi et al., 2012). For PEDOTrPSS, many secondary dopants, commonly called conductivity enhancement agents, such as, polyols, alcohols, surfactants, salts, acids, and organic solvents, have been widely used to enhance the electrical conductivity (McCarthy et al., 2014). It reached 2084 S cm with the use of a nonvolatile ionic liquid (Badre et al., 2012) and 3065 S cm or even higher after H2SO4 treatment at high temperature (Xia et al., 2012). 

Mengistie, D.A., Chen, C.-H., Boopathi, K.M., Pranoto, F.W., Li, L.-I., Chu, C.-W., 2014. Enhanced thermoelectric performance of PEDOT PSS flexible bulky papers by treatment with secondary dopants. ACS Appl. Mater. Interfaces 7,94-100. 

Secondary dopants, such as benzo-l,4-dioxan and quinoxaline, have been introduced and their action was... 

Srisuwan S, Ding Y, Mamangun D, Thongyai S, Praserthdam P, Sotzing GA, et al. Secondary dopants modified PEDOT-sulfonated poly (imide)s for high-temperature range application. J Appl Polym Sci 2013 128(6) 3840-5. 

Schottky barrier, 16-19 Schulz, 6-2, 6-6 SCL regime, 19-3 SCLC model, 16-9, 16-639 SCLC, 16-9, 16-19 Screw direction, 3-5-3-7, 3-8, 3-10 SDWs-(TMTSF)2PFg, 16-14-16-15 Secondary battery, 8-73-8-77 Secondary dopants for PEDT PSS, 10-9 Secondary growth, 7-7-7-11 Selected area electron diffraction, 17-32 Self-assembled monolayer (SAM), 8-55-8-56,... 

The solution to the problem of increasing the conductivity to above 10 S/cm, and doing this in a reproducible way has not been found in another variation of EB/special dopant/secondary dopant/ stretching , but on the following basis ... 

It should be noted that not only special dopants, but also secondary dopants are unnecessary, as we achieved such conductivity also with octanole as dispersion medium. This complex sequence of process steps is controlled by at least 80 different parameters (like temperatures, time, sequence of actions, additives, etc.). We have analyzed the effect of all of these parameters from the first to the last process step levels and determined the most important 25 parameters. These were the input into a neural network program [138] the neural network has been appropriately set up and optimized, and has heen trained in several series of training actions finally with the input of more than 400 fully documented experiments. 

B. D. Martin, N. Nikolov, S. K. PoUack, A. Saprigin, R. Shashidar, F. Zhang and P. A. Heiney, Hydroxylated secondary dopants for surface resistance enhancement in transparent poly(3,4-ethylene-dioxythiophene)-poly(styrenesulfonate) thin films, Synth. Met. 142 (1-3), 187-193 (2004). 

The N-methyl-2-pyrrolidone (NMP), which is a secondary dopant polymer helping to improve the conductivity of the final chemical formulation. 

N-methyl-2-pyrrolidone Secondary dopant Increase the conductivity... 

A secondary dopant is apparently an inert substance which, when applied to a primary-doped polymer, induces still further changes in the properties, including a further increase in conductivity. It differs from a primary dopant, in that the newly enhanced properties may persist even upon complete removal of the secondary dopant. 

Functionalized protonic acids such as ( ) camphor sulfonic acid (HCSA) and dodecyl benzene sulfonic acid (HDBSA) are used as primary dopants while m-cresol, xylene, etc. are used as the secondary dopants. The free-standing non-oriented PANI-CSA films cast from the above solvents have conductivities in the range 100—400 S cm , a value two orders of magnitude larger than that of non-oriented films of emeraldine base doped with aqueous HCl. MacDiarmid et al. [34] found that the conductivity of POT-CSA is 0.2 S cm in w-cresol and 2 S cm in chloroform whereas that of PANI-CSA is 140 S cm in w-cresol and 0.16 S cm in chloroform. These differences can be attributed as due to the interaction of the non-polar covalent methyl groups in POT with less polar chloroform, whereas in the case of RANI, the polar backbone can interact more readily with the polar /n-cresol. 

Phenomenologically, treatment of a polymer already doped by a primary dopant with an apparently inert substance (secondary dopant) may increase the conductivity of the polymer by several orders of magnitude with concomitant changes in the electronic spectra, and frequently in the degree of crystallinity. Secondary doping differs from primary doping, as mentioned earlier, in that the changes induced by primary/ secondary dopant combination employed may frequently persist, possibly to a reduced extent, even on removal of the secondary dopant. 

Influence of Water and "Secondary Dopants" on PAn crystallinity. An increase in crystallinity of PAn emeraldine salt has been reported by the incorporation of secondary plasticizing agents. Pron et al. have shown that... 

Recently, much interest has been shown in enhancing the order and consequent conducting properties of conducting polyaniline salts via postpolymerization treatment with an appropriate "secondary dopant." In particular, much attention has focused on the influence of w-cresol 1 solvent or... 

Occasionally, the term secondary dopant is used more loosely for a second redox treatment of a polymer chain that has already been subjected to a redox agent. Generally, the term is used, however, in the way as defined by MacDiarmid and Epstein and will therefore only be used in this more specific sense in this book. Also, the term conductivity enhancement agent is widely used as an alternative for the term secondary doping. 

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