Multiwall carbon nanotubes have been dispersed homogeneously throughout polystyrene matrices by a simple solution-evaporation method without destroying the integrity of the nanotubes. Tensile tests on composite films show that 1 wt % nanotube additions result in 36%-42% and ϳ25% increases in elastic modulus and break stress, respectively, indicating significant load transfer across the nanotube-matrix interface. In situ transmission electron microscopy studies provided information regarding composite deformation mechanisms and interfacial bonding between the multiwall nanotubes and polymer matrix. © 2000 American Institute of Physics. ͓S0003-6951͑00͒04120-6͔Carbon nanotubes ͑NTs͒ have many remarkable physical characteristics such as novel electronic properties, 1 exceptionally high axial strengths and axial Young's moduli of the order of terra pascal. [2][3][4] The exact magnitude of these properties depends on the diameter and chirality of the NT and whether they are in single-wall or multiwall form. Because of their outstanding physical properties, carbon nanotubes have numerous potential applications.5 One class of nanotube materials is NT composites in which the nanotube architecture is established within a host matrix material. Foreseeable NT-polymer composite materials include those designed for structural applications or for functional applications that make use of their conductivity, electromagnetic interference shielding 6,7 and optoelectronic properties. Large-scale production of NT composites will, of course, depend upon a large and inexpensive supply of high quality nanotubes. Several continuous chemical vapor deposition methods may hopefully meet this requirement in the near future. 9,10The effective utilization of nanotubes in composite applications depends strongly on the ability to disperse the NTs homogeneously throughout the matrix without destroying the integrity of the NTs. Furthermore, good interfacial bonding is required to achieve load transfer across the NT-matrix interface, a necessary condition for improving the mechanical properties of polymer composites. Polymer-NT composites have been the topic of several recent studies which used epoxy resins 6,11-15 and thermoplastic polymers 16,17 as the matrix materials. In these studies the important issue of NT dispersion was not, however, studied in great detail. In this letter, we address both nanotube dispersion and deformation mechanisms in polymer composites by studying a model composite system in which multiwall NTs ͑MWNTs͒ are dispersed in a polystyrene ͑PS͒ matrix. The homogeneity of the composites and deformation mechanisms are studied by in situ transmission electron microscopy ͑TEM͒.In this work we employed a simple solutionevaporation 18 method assisted by high-energy sonication to prepare uniform MWNT-PS composite samples. First, the PS ͑48 000 or 280 000 molecular weight from Aldrich Chemical Company, Inc.͒ was dissolved in toluene with a mass ratio of 1:10. The MWNTs were dispersed separately in toluene by high-energy sonication ...

Nanoscale structures that could mimic the selective transport and extraordinarily fast flow possible in biological cellular channels would have a wide range of potential applications. Here we show that liquid flow through a membrane composed of an array of aligned carbon nanotubes is four to five orders of magnitude faster than would be predicted from conventional fluid-flow theory. This high fluid velocity results from an almost frictionless interface at the carbon-nanotube wall.

An array of aligned carbon nanotubes (CNTs) was incorporated across a polymer film to form a well-ordered nanoporous membrane structure. This membrane structure was confirmed by electron microscopy, anisotropic electrical conductivity, gas flow, and ionic transport studies. The measured nitrogen permeance was consistent with the flux calculated by Knudsen diffusion through nanometer-scale tubes of the observed microstructure. Data on Ru(NH3)6(3+) transport across the membrane in aqueous solution also indicated transport through aligned CNT cores of the observed microstructure. The lengths of the nanotubes within the polymer film were reduced by selective electrochemical oxidation, allowing for tunable pore lengths. Oxidative trimming processes resulted in carboxylate end groups that were readily functionalized at the entrance to each CNT inner core. Membranes with CNT tips that were functionalized with biotin showed a reduction in Ru(NH3)6(3+) flux by a factor of 15 when bound with streptavidin, thereby demonstrating the ability to gate molecular transport through CNT cores for potential applications in chemical separations and sensing.

Nanoscale structures that could mimic the selective transport and extraordinarily fast flow possible in biological cellular channels would have a wide range of potential applications. Here we show that liquid flow through a membrane composed of an array of aligned carbon nanotubes is four to five orders of magnitude faster than would be predicted from conventional fluid-flow theory. This high fluid velocity results from an almost frictionless interface at the carbon-nanotube wall.

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