Gold nanoparticles were selectively attached to chemically functionalized surface sites on nitrogen-doped carbon (CN x ) nanotubes. A cationic polyelectrolyte was adsorbed on the surface of the nanotubes by electrostatic interaction between carboxyl groups on the chemically oxidized nanotube surface and polyelectrolyte chains. Negatively charged 10 nm gold nanoparticles from a gold colloid suspension were subsequently anchored to the surface of the nanotubes through the electrostatic interaction between the polyelectrolyte and the nanoparticles. This approach provides an efficient method to attach other nanostructures to carbon nanotubes and can be used as an illustrative detection of the functional groups on carbon nanotube surfaces.

The ability to modify the surface of carbon nanotubes is of crucial importance for their utilization in different applications. In the present paper we report on the chemical modification of multiwalled carbon nanotubes (MWNT) by means of epoxide-based functional groups. MWNT were first carboxylated along their walls. This was followed by further reactions to attach di-glycidyl ether of bisphenol-A-based epoxide resin. The behavior of the modified nanotubes in various solvents was altered due to the chemical changes, and analytical techniques were utilized to detect the chemical attachments. The implications of the surface modification achieved are discussed primarily in terms of nanotube−polymer composite applications.

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A series of observations of polymer sheathing in multiwalled carbon nanotube (MWCNT)−polycarbonate composites are presented. This sheathing was observed in images of the composite fracture surface and is consistent with diameter distributions of the as-received and embedded MWCNTs. A novel nanomanipulation experiment, where the sheathing balls up when contacted by an AFM tip, confirms this phenomenon. This sheathing layer is direct evidence of substantial MWCNT−polymer interaction and will influence the mechanical properties of MWCNTpolymer composites.Due to the outstanding physical properties of carbon nanotubes, intense activity is being devoted to the development of carbon nanotube-polymer composites.1 Specifically, carbon nanotube-reinforced polymer composites have demonstrated high strength and stiffness, 2 which suggest their potential use as alternative materials for structural applications. Multifunctional nanotube-polymer composites are also under development, where in addition to improved mechanical properties, increases in electrical conductivity 3 and improved thermal properties 4 are obtained with small amounts of embedded nanotubes.One of the significant differences between micron-sized carbon fiber-filled polymers and nanotube-filled polymers is the large interfacial area of the nanotubes. This interfacial area provides an opportunity for altering the mobility and properties of a significant volume of polymer near the interface (i.e., the interphase region). Both the interface and interphase regions will play key roles in optimizing load transfer between the nanotube and the polymer matrix. While for traditional composites a variety of experimental techniques have been developed in an effort to quantify the fibermatrix interface, 5 for nanotube-polymer composites these tests are exceedingly difficult because of the small size of the nanotubes. In the process of developing nanoscale pullout tests of individual multiwalled carbon nanotubes from a polymer matrix, we have found several forms of evidence that suggest multiple polymer layers sheath the embedded nanotubes. This polymer sheathing is consistent with models of a nonbulk polymer interphase region that has been identified in nanotube-polymer composite systems. 6 The results presented in this paper are consistent with the findings of other researchers regarding the existence of intimate MWCNT-polymer interaction in nanotubepolymer composites. For example, strong polymer adherence has been reported in previous TEM studies of nanotubepolymer nanocomposite samples.7 Potschke et al. studied the rheological behavior of nanotube-polycarbonate composites, and their SEM observation of the fracture surface showed that the apparent nanotube diameters at the fracture surface were larger than the diameters of the original carbon nanotube material, indicating significant polymer wetting on the nanotube surface. 8 However, to date a detailed study of this polymer sheathing phenomenon in carbon nanotubepolymer nanocomposites has not been undertaken. ...