Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Nanocomposites of poly (methyl methacrylate) (PMMA) and carbon nanotubes have a high potential for applications where conductivity and low specific weight are required. This piece of work concerns investigations of the level of dispersion and morphology on the electrical properties of in situ polymerized nanocomposites in different concentrations of multi-walled carbon nanotubes (MWCNT) in a PMMA matrix. The electrical conductivity was measured by the four point probe. The morphology and dispersion was analyzed by Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS). The correlation between electrical conductivity and the MWCNT amount, presented a typical percolation behavior, whose electrical percolation threshold determined by power law relationship was 0.2 vol. (%) The exponent t from the percolation power law indicated the formation of a 3D network of randomly arranged MWCNT. SAXS detected that the structures are intermediate to disks or spheres indicating fractal geometry for the MWCNT aggregates instead of isolated rods. HR-TEM images allowed us to observe the MWCNT individually dispersed into the matrix, revealing their distribution without preferential space orientation and absence of significant damage to the walls. The combined results of SAXS and HR-TEM suggest that MWCNT into the polymeric matrix might present interconnected aggregates and some dispersed single structures.17 127132CNPq; Conselho Nacional de Desenvolvimento Científico e TecnológicoConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Bauhofer, W., Kovacs, J.Z., A review and analysis of electrical percolation in carbon nanotube polymer composites (2009) Composites Science and Technology, 69 (10), pp. 1486-1498. , http://dx.doi.org/10.1016/j.compscitech.2008.06.018Hori, M., Aoki, T., Ohira, Y., Yano, S., New type of mechanical damping composites composed of piezoelectric ceramics, carbon black and epoxy resin (2001) Composites Part A: Applied Science and Manufacturing, 32 (2), pp. 287-290. , http://dx.doi.org/10.1016/S1359-835X(00)00141-XMarcq, F., Demont, P., Monfraix, P., Peigney, A., Laurent Ch., Falact, T., Carbon nanotubes and silver flakes filled epoxy resin for new hybrid conductive adhesives (2011) Microelectronics Reliability, 51 (7), pp. 1230-1234. , http://dx.doi.org/10.1016/j.microrel.2011.03.020Li, C., Liang, T., Lu, W., Tang, C., Hu, X., Cao, M., Improving the antistatic ability of polypropylene fibers by inner antistatic agent filled with carbon nanotubes (2004) Composites Science and Technology, 64 (13-14), pp. 2089-2096. , http://dx.doi.org/10.1016/j.compscitech.2004.03.010Chung, D.D.L., Review: Electromagnetic interference shielding effectiveness of carbon materials (2001) Carbon, 39 (2), pp. 279-285. , http://dx.doi.org/10.1016/S0008-6223(00)00184-6Sanjinésa, R., Abadb, M.D., Vâjua, C.R., Smajdaa, R., Mionića, M., Magreza, A., Electrical properties and applications of carbon based nanocomposite materials: An overview (2011) Surface and Coatings Technology, 206 (4), pp. 727-733. , http://dx.doi.org/10.1016/j.surfcoat.2011.01.025Iijima, S., Helical microtubules of graphitic carbon (1991) Nature, 354, pp. 56-58. , http://dx.doi.org/10.1038/354056a0Treacy, M.M.J., Ebbesen, T.W., Gibson, J.M., Exceptionally high Young's modulus observed for individual carbon nanotubes (1996) Nature, 381, pp. 678-680. , http://dx.doi.org/10.1038/381678a0Saito, R., Dresselhaus, G., Dresselhaus, M.S., (1998) Physical Properties of Carbon Nanotubes, , London: Imperial College PressWei, C., Cho, K., Srivastava, D., Tensile strength of carbon nanotubes under realistic temperature and strain rate (2003) Physical Review B, 67 (11), pp. 115407-115412. , http://dx.doi.org/10.1103/PhysRevB.67.115407Vaia, R.A., Wagner, H.D., Framework for nanocomposites (2004) Materials Today, 7 (11), pp. 32-37. , http://dx.doi.org/10.1016/S1369-7021(04)00506-1Ma, P.C., Siddiqui, N.A., Marom, G.J., Kim, K., Dispersion and functionalization of carbon nanotubes for polymer-based nanocomposites: A review (2010) Composites Part A: Applied Science and Manufacturing, 41 (10), pp. 1345-1367. , http://dx.doi.org/10.1016/j.compositesa.2010.07.003Lux, F., Models proposed to explain the electrical conductivity of mixtures made of conductive and insulating materials (1993) Journal of Materials Science, 28 (2), pp. 285-301. , http://dx.doi.org/10.1007/BF00357799Strümpler, R., Glatz-Reichenback, J., Conducting polymers composites (1999) Journal of Electroceramics, 3 (4), pp. 329-346. , http://dx.doi.org/10.1023/A:1009909812823Ponomarenko, A.T., Shevchenko, V.G., Enikolopyan, N.S., Formation processes and properties of conducting polymer composites (1990) Advances in Polymer Science, 96, pp. 125-147. , http://dx.doi.org/10.1007/3-540-52791-5_4Hernández, J.J., García-Gutiérrez, M.C., Nogales, A., Rueda, D.R., Ezquerra, T.A., Small-angle x-ray scattering of single-wall carbon nanotubes dispersed in molten poly(ethylene terephthalate) (2006) Composites Science and Technology, 66 (15), pp. 2629-2632. , http://dx.doi.org/10.1016/j.compscitech.2006.05.008García-Gutiérrez, M.C., Nogales, A., Hernández, J.J., Rueda, D.R., Ezquerra, T.A., X-ray scattering applied to the analysis of carbon nanotubes, polymers and nanocomposites (2007) Óptica Pura y Aplicada, 40 (2), pp. 195-205Martin, J.E., Hurd, A.J., Scattering from fractals (1987) Journal of Applied Crystallography, 20 (2), pp. 61-78. , http://dx.doi.org/10.1107/S0021889887087107Rols, S., Almairac, R., Henrard, L., Anglaret, E., Sauvajol, J.L., Diameter distribution of single wall carbon nanotubes in nanobundles (2000) European. 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