Since their discovery [1] , intrinsically conducting polymer s ( ICP s) have changed our way of thinking about polymers. With properties such as light weight, organic functionality, and distinctive electronic behavior, new applications were soon devised for these materials. Polyaniline ( PANI ) is one of the most interesting ICPs because of its chemical stability, tunable conductivity, and interesting electrochromic behavior [2] . This polymer is usually synthesized by chemical oxidation of the monomer in strong acidic media. Besides PANI, polythiophenes and polypyrrole are other important ICPs that have also been synthesized by oxidative polymerization. These polymers have been extensively used in several applications in the fi elds of organic electronics [3] , sensors [4] , actuators [5] , separation technologies [6] , and energy storage [7] , among others, and new applications for them are found continuously.Enzymatic polymerizations have become an interesting alternative route for polymer synthesis [8] . They are generally carried out under milder conditions than similar synthetic routes. Enzymes are natural catalysts which are non -toxic, biodegradable, energy effi cient and obtained from renewable resources. In this chapter, we review the different strategies that have been used for the enzymatic synthesis of PANI. Xu et al .[9] reviewed published work regarding enzymatic polymerization of aniline derivatives from its beginning until 2004. However, more recently, several groups have developed either new approaches for the enzymatic synthesis of PANI or different methods inspired by it. Indeed, the infl uence of the enzymatic synthesis of PANI can be seen in the development of several biocatalytic and biomimetic synthetic routes not only for the synthesis of PANI, but also for other important conductive polymers, such as polypyrrole ( PPy ) and poly(3,4 -ethylendioxythiophene) ( PEDOT ).

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There has been much interest in the last few years on materials reinforced with nanometer scale particles. These so-called nanocomposites can exhibit hybrid properties derived from its components. One of the most promising nanocomposites is that based on polymers reinforced with single-layered carbon sheets named graphene. The reason is that graphene can significantly improve the physical properties of the polymeric material once it is completely dispersed in the matrix. In this work nylon/graphene nanocomposites were prepared starting from the synthesis of graphite oxide (GO). Direct oxidation of graphite powder was utilized to produce GO. That is, the oxidation reaction produced graphite layers with functional groups containing oxygen. The aim was to increase the polarity of GO to enable a good dispersion in polar solvents. Then, nylon/graphene nanocomposites were prepared by reducing GO in the presence of nylon. Finally, non-woven membranes, with nanometer sized filaments, of nylon/graphene were electrospun. The morphology and microstructure of the nanocomposites was investigated via electron microscopy and X-ray diffraction.

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Ultra-high molecular weight polyethylene/graphite nanocomposites were prepared by high-energy cryogenic milling followed by syntering. Microstructure changes shows that graphite was reduced to graphite nanoplatelets by high-energy cryomilling and partial exfoliation of graphite to few layered graphene nanoplatelets occurred in a small extent. The resulting nanocomposites revealed high electrical conductivity and good mechanical performance. Thermal characterization of the nanocomposites was also carried out by differential scanning calorimetry.