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Two materials, pure poly(acrylic acid) (PAA) and nanocomposites with a matrix of PAA and carbon nanotubes (CNTs) as reinforcing agent were synthesized by semi-continuous heterophase polymerization (SHP). CNTs were prepared by a chemical vapor deposition technique and purified by steam. CNTs were characterized by a high resolution scanning electron microscopy (HRSEM) and Raman and Fourier transform infrared spectroscopies. Nanocomposites were prepared with: (i) purified CNTs (CNTsp) or (ii) purified and functionalized CNTs possessing an acyl chloride moiety (CNTsOCl). In both cases, the nanocomposites synthesis was carried out byin situpolymerization of acrylic acid (AA) by SHP. When CNTsOClwere used previously to the polymerization of AA, a series of specific amounts of CNTsOCland AA were mixed to induce a chemical reaction between the carboxyl group of AA and the acyl chloride group of the CNTsOCl. The product, acrylic acid grafted to CNTsOCl(CNTsOCl-AA), was used to prepare the PAA-CNTsOClnanocomposites. The PAA-CNTsOClnanocomposites were characterized by HRSEM, Raman, FTIR and CPMAS13C-NMR spectroscopies and also by thermogravimetric analysis (TGA). The results reveal that PAA-CNTsOClnanocomposites were formed by PAA macromolecules grafted to CNTsOCl. The kinetic behavior observed for the synthesis of pure PAA or PAA-CNTsOClnanocomposites by SHP was similar. Latexes of PAA-CNTsOClnanocomposites were stable without formation of a precipitate of CNTsOClfor over 1.5 years, while latex prepared with CNTspand PAA, was unstable and formation of a precipitate of CNTspwas observed immediately after its preparation. PAA-CNTspnanocomposites were characterized only by TGA. Moreover, latex of the PAA-CNTspnanocomposite that did not precipitate immediately after its preparation, turned into a gel; this gelation never occurred with the PAA-CNTsOClnanocomposite latex. [ABSTRACT FROM PUBLISHER]