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Science 24 March 2006:
Vol. 311. no. 5768, pp. 1740 - 1743
DOI: 10.1126/science.1122225
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Reports

General Strategies for Nanoparticle Dispersion

Michael E. Mackay,1,2* Anish Tuteja,1 Phillip M. Duxbury,2 Craig J. Hawker,3,4 Brooke Van Horn,4 Zhibin Guan,5 Guanghui Chen,5 R. S. Krishnan1

Traditionally the dispersion of particles in polymeric materials has proven difficult and frequently results in phase separation and agglomeration. We show that thermodynamically stable dispersion of nanoparticles into a polymeric liquid is enhanced for systems where the radius of gyration of the linear polymer is greater than the radius of the nanoparticle. Dispersed nanoparticles swell the linear polymer chains, resulting in a polymer radius of gyration that grows with the nanoparticle volume fraction. It is proposed that this entropically unfavorable process is offset by an enthalpy gain due to an increase in molecular contacts at dispersed nanoparticle surfaces as compared with the surfaces of phase-separated nanoparticles. Even when the dispersed state is thermodynamically stable, it may be inaccessible unless the correct processing strategy is adopted, which is particularly important for the case of fullerene dispersion into linear polymers.

1 Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824, USA.
2 Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA.
3 Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA.
4 IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120, USA.
5 Department of Chemistry, University of California, Irvine, CA 92697, USA.

* To whom correspondence should be addressed. E-mail: mackay{at}msu.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Nanoparticle Polymer Composites: Where Two Small Worlds Meet..
A. C. Balazs, T. Emrick, and T. P. Russell (2006)
Science 314, 1107-1110
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Science. ISSN 0036-8075 (print), 1095-9203 (online)