85 ISSN 1811-2382, Polymer Science, Series C, 2016, Vol. 58, No. 1, pp. 85–92. © Pleiades Publishing, Ltd., 2016. Original Russian Text © E.A. Karpushkin, A.K. Berkovich, V.G. Sergeyev, 2016, published in Vysokomolekulyarnye Soedineniya, Ser. C, 2016, Vol. 58, No. 1, pp. 93–101. Composites Based on Acrylic Polymers and Carbon Nanotubes as Precursors of Carbon Materials E. A. Karpushkin a, b *, A. K. Berkovich a , and V. G. Sergeyev a a Faculty of Chemistry, Moscow State University, Moscow, 119899 Russia b Bauman Moscow State Technical University, ul. Vtoraya Baumanskaya 5, str. 1, Moscow, 105005 Russia *е-mail: eukarr@gmail.com Received November 12, 2015 Abstract—The effect of carbon nanotubes on the properties of composite fibers and films based on polyacry- lonitrile is analyzed. It is shown that the introduction of carbon nanotubes makes it possible to improve the mechanical characteristics of the composite material. Data on the effect of carbon nanotubes on chemical reactions occurring during the thermal stabilization and carbonization of these materials are cited. DOI: 10.1134/S1811238216010057 INTRODUCTION Since their discovery in 1991 [1], carbon nanotubes (СNTs) have attracted the attention of researchers because of their unique set of mechanical (rigidity, strength, and record values of elastic modulus), elec- tric, and optical properties [2]. Depending on their structural features, СNTs are divided into single-wall and multiwall (composed of several embedded single- wall СNTs) as well as chiral and achiral. The amount of layers constituting СNTs largely determines their mechanical properties, whereas chirality, structural imperfection, and the presence of amorphous carbon on the surfaces of nanotubes primarily affect their chemical and electronic properties [2]. Recent studies have shown that the use of СNTs as a filler of polymeric materials allows efficient control over the mechanical [3] and electric [4] properties of these materials because СNTs are characterized by high length-to-diameter ratios (1000 or greater). Spe- cifically, СNTs have been employed as an additive to polyacrylonitrile for the creation of new-generation carbon fibers [5]. As precursors of carbon fibers, copolymers of acrylonitrile with small amounts of methyl acrylate and itaconic or acrylic acid are used. At present, exactly these copolymers are applied to produce carbon fibers with record values of strength (6.37 GPa [6]) and elastic modulus (up to 294 GPa [6]) that are employed as reinforcing components of modern composite materials [7]. The mechanical properties of СNTs are almost an order of magnitude higher than those of carbon fibers; therefore, СNTs hold much promise for the design new-generation composite materials. The extensive studies of СNT-containing spin dopes of PAN and composite fibers formed on their basis commenced not long ago [8–10]. It has been found that the addition of carbon nanotubes to a spin dope considerably simplifies heat treatment of the PAN fiber and improves the quality of the final carbon fiber [11–13]. However, as has been mentioned in [14, 15], the introduction of СNTs into a PAN fiber insig- nificantly affects the heat treatment of the fiber and does not improve the properties of the final product. In other words, the introduction of СNTs only unrea- sonably complicates the technological scheme of car- bon fiber production and does not provide any advan- tages. The seeming inconsistency may be due to the fact that the advantageous effect of СNTs on the process of heat treatment of the PAN fiber and properties of the final product is related not directly to the properties of СNTs but to change in the structure and properties of the polymer solution caused by the introduction of the anisotropic filler into it and/or the effect of this filer on chemical processes occurring during the heat treat- ment of composite PAN-based materials. This review will address some factors that, in our opinion, are the most important in explaining the inconsistency of the published data. DISPERSION OF СARBON NANOTUBES IN A PAN SOLUTION: PREPARATION, STRUCTURE, AND RHEOLOGICAL BEHAVIOR The dispersions of СNTs in PAN solutions were apparently first described in [16]. Already at that point it was indicated that the associates of CNTs (Fig. 1a) should be destroyed to obtain stable homogeneous dispersions. Otherwise, the sedimentation-unstable dispersion with separated microphases is formed.