The water-dispersed conductive polypyrrole (PPy) was prepared via the in situ oxidative chemical polymerization by using ammonium persulfate (APS) as oxidant and tunicate cellulose nanocrystals (T-CNs) as a dopant and template for tuning the morphologies of PPy nanoparticles. Highly flexible paper-like materials of PPy/T-CNs nanocomposites with high electrical conductivity values and good mechanical properties were prepared. The structure of nanocomposites of PPy/T-CNs was investigated by using Fourier transform infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy analyses of the composites revealed that PPy consisted of nanoparticles about 2.5？nm in mean size to form a continuous coating covered on the T-CNs. The diameters of the PPy nanoparticles increased from 10 to 100？nm with the increasing pyrrole amount. Moreover, electrical properties of the obtained PPy/T-CNs films were studied using standard four-probe technique and the electrical conductivity could be as high as 10？3？S/cm. 1. Introduction The demand for new technologies that require high performance materials has driven materials research towards the development of novel functional nanoscaled materials with superior properties. Conducting polymers are a promising class of materials that possess unique properties that allow them to be used in a wide variety of applications [1]. The conductive properties of polyacetylene resulted in the 2000 Nobel Prize in chemistry and various analogues of it have been investigated throughout the years including polyphenylene, polyaniline, polythiophene, and polypyrrole [2]. PPy, one of the most prominent types of conjugated polymers, is a promising conducting polymer in electronics and biological and medical areas due to its straightforward polymerization, environmental stability, and high electrical conductivity that can be controlled by changing the doping degree [3]. But the poor processability and inadequate mechanical properties limit its commercial applications. In order to overcome these problems, several processing methods have been studied. The first approach toward PPy nanoparticles was reported by Bjorklund and Liedberg, who polymerized pyrrole in water in the presence of methyl cellulose. Particles of 100？nm to 200？nm size were observed in films spread from the reaction mixture [4]. Arms and Vincent prepared colloidally stable dispersions of PPy nanoparticles by aqueous dispersion polymerization in the presence of polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) as a stabilizer [5]. PPy spherical
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