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Science 16 October 2009:
Vol. 326. no. 5951, pp. 408 - 410
DOI: 10.1126/science.1177114
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Reports

The Packing of Granular Polymer Chains

Ling-Nan Zou,1,* Xiang Cheng,1,2 Mark L. Rivers,3 Heinrich M. Jaeger,1 Sidney R. Nagel1

Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here, we examine the disordered packing of chains constructed out of flexibly connected hard spheres. Using x-ray tomography, we find that long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally, we uncover close similarities between the packing of chains and the glass transition in polymers.

1 The James Franck Institute and Department of Physics, University of Chicago, Chicago, IL 60637, USA.
2 Department of Physics, Cornell University, Ithaca, NY 14853, USA.
3 Department of Geophysical Sciences and Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, USA.

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

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
A Ball-and-Chain Polymer Model.
C. J. O. Reichhardt and L. M. Lopatina (2009)
Science 326, 374-375
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Science. ISSN 0036-8075 (print), 1095-9203 (online)