Semi-Continuous Heterophase Polymerization to Synthesize Nanocomposites of Poly(acrylic acid)-Functionalized Carbon Nanotubes

• Published in: Journal of macromolecular science. Part A, Pure and applied chemistry Pure and applied chemistry, 2015-09, Vol.52 (9), p.732-744
• Main Authors: Silva-Jara, J. M., Manríquez-González, R., López-Dellamary, F. A., Puig, J. E., Nuño-Donlucas, S. M.
• Format: Article
• Language: English
• Subjects: carbon nanotubes; Nanocomposites; poly(acrylic acid); semi-continuous heterophase polymerization
• ISSN: 1060-1325; 1520-5738
• DOI: 10.1080/10601325.2015.1063873

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 (CNTs p ) or (ii) purified and functionalized CNTs possessing an acyl chloride moiety (CNTs OCl ). In both cases, the nanocomposites synthesis was carried out by in situ polymerization of acrylic acid (AA) by SHP. When CNTs OCl were used previously to the polymerization of AA, a series of specific amounts of CNTs OCl and AA were mixed to induce a chemical reaction between the carboxyl group of AA and the acyl chloride group of the CNTs OCl . The product, acrylic acid grafted to CNTs OCl (CNTs OCl -AA), was used to prepare the PAA-CNTs OCl nanocomposites. The PAA-CNTs OCl nanocomposites were characterized by HRSEM, Raman, FTIR and CPMAS 13 C-NMR spectroscopies and also by thermogravimetric analysis (TGA). The results reveal that PAA-CNTs OCl nanocomposites were formed by PAA macromolecules grafted to CNTs OCl . The kinetic behavior observed for the synthesis of pure PAA or PAA-CNTs OCl nanocomposites by SHP was similar. Latexes of PAA-CNTs OCl nanocomposites were stable without formation of a precipitate of CNTs OCl for over 1.5 years, while latex prepared with CNTs p and PAA, was unstable and formation of a precipitate of CNTs p was observed immediately after its preparation. PAA-CNTs p nanocomposites were characterized only by TGA. Moreover, latex of the PAA-CNTs p nanocomposite that did not precipitate immediately after its preparation, turned into a gel; this gelation never occurred with the PAA-CNTs OCl nanocomposite latex.