The interaction between poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and cellulosic fibers was characterized in order to obtain further understanding of the conductivity properties of the modified cellulosic fiber material. Microcrystalline cellulose (MCC) was used as a model surface to study the adsorption behavior at various pH and salt concentrations, while samples of low-conductivity paper, normally used for the production of electrical insulation papers, were dipped into PEDOT:PSS dispersion and air-dried for X-ray photoelectron spectroscopy (XPS) studies. The results showed a strong interaction between the MCC and PEDOT:PSS, which implied a broad molecular distribution of the conducting polymer. With increasing pH, less amount of the conducting polymer was adsorbed whereas the amount adsorbed passed through a maximum value with varying salt concentration. Zeta potential measurement and polyelectrolyte titration were used to determine the surface charge of both suspended MCC particles and dispersed PEDOT:PSS at various pH levels and salt concentrations. Dip-coated paper samples exhibited two peaks in the S(2p) XPS spectra at 168-169 and 164-165 eV which correspond to the sulfur signals of sulfonate (in PSS) and in thiophene (in PEDOT), respectively. It was found that the PEDOT:PSS with a ratio of 1:2.5 was adsorbed more in the base paper than that with a ratio of 1:6. The PEDOT:PSS ratio on the surface of the cellulosic material was higher than that in the bulk liquid for all samples. The results indicated that PEDOT was preferentially adsorbed rather than PSS. The degree of washing of the conducting polymer did not significantly affect the PEDOT enhancement on the surface.

Electroconductive papers were produced by coating commercial base papers with blends of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT:PSS) and organic solvents. The bulk conductivities of the coated papers were measured using a fourprobe technique. One-sided and two-sided coating gave comparable conductivity levels. The presence of sorbitol and isopropanol in the PEDOT:PSS blends did not enhance the bulk conductivity of the coated paper, and with increasing concentrations of these solvents, the conductivity decreased due to dilution of the conducting component. Samples coated with PEDOT:PSS blends containing N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) exhibited a higher conductivity than those coated with pure PEDOT:PSS because of their plasticizing effect and conformational changes of PEDOT molecules indicated by the red shift and disappearance of the shoulder peak at about 1442 cm À1 in the Raman spectra of the coated samples. EDS imaging showed that PEDOT:PSS is distributed throughout the thickness direction of the paper. Contact angle measurements were made to monitor the hydrophilicity of the paper surface and total sulfur analysis was used to determine the amount of PEDOT:PSS deposited onto the paper. The tensile strength of all the paper samples increased slightly after treatment. Thus, it is demonstrated that enhanced bulk conductivity in the order of 10 À3 S/cm can be achieved by using organic conductive materials and surface treatment techniques.

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Multiwall carbon nanotubes (MWCNT) were added to a dispersion of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)-dimethyl sulfoxide (DMSO) at various dosage levels (0.1, 0.3, 0.5 wt %). The mixture was characterized in terms of its rheological behavior, and a difference was observed between ultrasonicated and nonultrasonicated mixtures. All the dispersions exhibited shear thinning behavior. Ultrasonication helped to minimize the aggregation of nanotubes in the dispersion. Coating the dispersions onto a commercial base paper on both sides turned the paper into a moderately conductive material with a bulk conductivity level of 10 À3 S/cm. The proposed equivalent circuits of the coated papers which were derived from the Nyquist plot of the Impedance Spectroscopy data consist of a resistor connected in parallel to a capacitor. Likewise, the Bode plot showed the behavior of the complex impedance and phase angle of the coated paper as a function of frequency. The I-V characteristic and the bulk conductivity values of the paper samples are reported. Scanning Electron Microscopy (SEM)-Energy dispersive spectroscopy showed the deposition of the conducting polymer in the fiber network. The tensile indices of all coated papers were slightly higher than that of the base paper. Apart from altering the conductive properties of the paper, opening the way to new uses of the paper, the equivalent circuit behavior of the modified paper allows for the development of other functions, such as sensors or energy storage. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 125: E34-E40, 2012