1. Field of the Invention
This invention relates to fullerene-polymer compositions produced by combining a sufficient amount by weight of fullerenes to result in a change or modification of the viscoelastic properties compared to the unmodified polymer. Typically, such amount from about 0.01 to about 85 percent by weight of fullerenes in comparison to the weight of the polymer. This invention also relates to the process of making the compositions and the method of using the compositions, and includes the products produced by the process disclosed herein.
2. Discussion of Related Art
Fullerenes are hollow molecules composed only of carbon atoms which constitute a new allotropic form of carbon. Typically, fullerenes each have carbon atoms arranged as 12 pentagons, but differing numbers of hexagons. The pentagons are required in order to allow the curvature and eventual closure of the closed surface upon itself. The most abundant species of fullerene identified to date is the C.sub.60 molecule or Buckminsterfullerene. C.sub.60 consists of 12 pentagons and 20 hexagons and is classified as an icosahedron, the highest symmetry structure possible. The second most abundant species classified to date is C.sub.70 and contains 12 pentagons and 25 hexagons. Characteristic of fullerenes is their general formula C.sub.2n where n is greater than 15. Fullerenes containing from 32 to many hundreds carbon atoms have been produced from carbon soots and detected by mass spectrometry. For further information concerning the structure of fullerenes, see, e.g., H. W. Kroto, et al., 91 CHEMICAL REVIEWS, 1213-1235 (1991). As used in this application, the terms "fullerene" and "fullerenes" means the 60 atom carbon molecule and all other hollow molecules composed only of carbon atoms. The term "higher fullerene" means fullerenes having the general formula C.sub.2n where n is greater than 30.
Other allotropic forms of carbon have been used in combination with polymers to improve the properties of the polymers; e.g., carbon fibers, carbon black. For further information concerning the use of other forms of carbon to enhance or modify the properties of polymers, see, e.g., G. Kraus, Reinforcement of Elastomers, Interscience Publishers, N.Y., 1965. These carbon structures typically contain minor amounts of other atoms such as hydrogen, oxygen and/or nitrogen and have the carbons arranged in quasi-graphitic layered planes. Carbon black, which is used extensively to modify the mechanical properties of polymers, particularly elastomeric polymers with glass transition temperatures of less than about O.degree. C., is prepared by incomplete combustion or thermal cracking of hydrocarbons. The resulting chemical structure and size of carbon black particles is, therefore, unlike that of fullerenes.
It has been disclosed that fullerenes could be polymerized into a polymer backbone along with unspecified comonomers to produce a polymer chain containing a fullerene unit. See Amato, Science 254, pp. 30-31 (1991). However, the disclosure does not teach the fullerene-polymer compositions of the present invention.