Functionalization of carbon nanotubes with arenedyazonium salts in urea
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Functionalization of carbon nanotubes with arenedyazonium salts in urea Oxana V.Kharissova, H.Leija, E.G. de Casas-Ortiz Universidad Autónoma de Nuevo León, Ciudad Universitaria s/n, San Nicolás de los Garza, N.L., Mexico,C.P. [email protected] ABSTRACT The functionalization of single wall carbon nanotubes (SWCNT) with arenediazonium salts, formed in situ from anilines as dimethyl-5-aminoisophthalate, sulfanilamide and p-anisidine, using the environmentally solvent urea. The functionalized SWNTs were then characterized using spectroscopic and microscopic methods along with thermogravimetric analysis (TGA). According to enhance solubility in solvents after that introduce them into the industrial processes. The molecules added appear on the nanotubes like chemical anchors. INTRODUCTION The single wall carbon nanotubes (SWCNTs) are widely used in development of novel materials, applied in nanotechnology [1-2]. However, a very common problem in their use is the dispersion of SWCNTs in different composite matrices, for instance polymer matrices; in addition, maintaining an efficient interaction between the SWCNTs and guest material [3]. So, the modification and control of SWCNTs properties via their functionalization with organic compounds forming covalent bonds with nanotubes are the area of significant importance [4]. Such functionalization increases their solubility in solvents creating facilities to be incorporated in industrial processes. In this work, we describe a simple and efficient process of covalent functionalization of SWCNTs with aryl dyazonium salts in an in situ process using a molten urea as a reaction medium [5]. The resulting functionalized nanotubes present a considerable increase in solubility in water and different organic solvents. EXPERIMENTAL The functionalization process SWCNTs with aryl dyazonium salts by melting of urea at 140°C (figure 1) shows the functionalization method applied. A mixture of 50 g (4.2 mmol) of SWCNTs and 60 g of urea (250% excess) is prepared in a flask, and then heated in oil bath to reach a temperature of 140°C. The SWCNTs are homogenized for 5 min, then 16.8 mmol of aniline are added, stirred for 5 min under nitrogen atmosphere. After sodium nitrite (1.6 g, 16.8 mmol) are added, leading to an exothermic reaction maintaining working temperature 140oC under constant magnetic stirring and nitrogen atmosphere for 15 min (Figure 2a).
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Figure 1. Scheme of funcionalization of SWCNT in molten urea with dyazonium salts formed in situ. A) dimethyl-5-aminoisophthalate, B) sulfanilamide y C) p-anisidine.
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Figure2. a) Functionalization process of SWCNTs with aryldiazonium salts in the medium of molten urea; b) functionalized carbon nanotube film (black color) in the membrane. The functionalized nanotubes of carbon were then purified with water and washed in ethanol, using a PTFE membrane of 0.45 μm for filtrate. For the last, the sample was washed in acetone using the same type of membrane (Figure 2b).
RESULTS AND DISCUSSION There are several analytical techniques
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