Intel Corporation (Santa Clara, CA) earned U.S. Patent 7,700,943 for its technique to functionalize carbon nanotubes in situ. A carbon nanotube (CNT) array is grown or deposited on a substrate. The CNT array is functionalized in situ with a polymer by partial thermal degradation of the polymer to form a CNT structure, according to inventors Nachiket R. Raravikar and James C Matayabas, Jr.
Carbon nanotubes are promising elements in nanotechnology. They are fullerene-related structures which consist of graphene cylinders. Applications that may be benefited using carbon nanotubes include high thermal conductivity materials for future packaging thermal demands, and highly sensitive materials for bio-recognition, and for in situ biochemical reactions on a bio-/micro-electronic chip. Such applications require an effective in-situ functionalization of carbon nanotubes.
Existing techniques for covalent or non-covalent functionalization of carbon nanotubes are insufficient to meet the above demands. In acid treatments, the vigorous acid sonication techniques introduce defects in the nanotube surface and are not in situ either. Anionic polymerization may be carried out in situ. But it needs a very careful control over chemistry, and is time consuming. Direct functionalization of polymers or larger radicals onto the nanotubes using plasma treatment has not been demonstrated yet. Currently there are no known strategies for in situ functionalization of nanotubes with polymer macro-radicals.
The Intel technique functionalizes carbon nanotubes in situ by partial thermal degradation of polymer around the nanotubes. The functionalized NTs with polymer macro-radicals may have numerous applications including composites for thermal management, micro-fluidics, bio-sensing, and bio-recognition. Nanotubes are known to scavenge and stabilize the polymer macro-radicals formed during the polymer thermal degradation process. This may be observed in terms of an increase in activation energy for degradation of polymer close to the CNT surface, as compared to the pure polymer. The thermal degradation temperature of such polymer is typically higher than that of the pure, bulk polymer. The interaction of CNTs with polymer macro-radicals during the early stage of polymer degradation indicates that there is a covalent or non-covalent bond between the macro-radicals with the CNT surface.
The technique utilizes this mechanism for surface modification of the CNTs. Subsequently, these functionalized NTs may be mixed with the same or different polymer to make composites, using processes such as melt mixing, solvent mixing, or in-situ polymerization into aligned CNT arrays. CNT composites may also be formed by functionalizing metals onto the CNTs, followed by infiltration of solders into the CNT arrays. Bio-molecules may also be immobilized onto the functionalized CNT assemblies to be used in bio-chips for bio-molecular recognition, bio-sensing, and in-situ biochemical reactions.