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Science 6 February 2009:
Vol. 323. no. 5915, pp. 757 - 760
DOI: 10.1126/science.1164601
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Reports

Confined Crystallization of Polyethylene Oxide in Nanolayer Assemblies

Haopeng Wang,1 Jong K. Keum,1 Anne Hiltner,1* Eric Baer,1 Benny Freeman,2 Artur Rozanski,3 Andrzej Galeski3

The design and fabrication of ultrathin polymer layers are of increasing importance because of the rapid development of nanoscience and nanotechnology. Confined, two-dimensional crystallization of polymers presents challenges and opportunities due to the long-chain, covalently bonded nature of the macromolecule. Using an innovative layer-multiplying coextrusion process to obtain assemblies with thousands of polymer nanolayers, we discovered a morphology that emerges as confined polyethylene oxide (PEO) layers are made progressively thinner. When the thickness is confined to 20 nanometers, the PEO crystallizes as single, high-aspect-ratio lamellae that resemble single crystals. Unexpectedly, the crystallization habit imparts two orders of magnitude reduction in the gas permeability.

1 Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106–7202, USA.
2 Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78758, USA.
3 Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, 90-363 Lodz, Poland.

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

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Science. ISSN 0036-8075 (print), 1095-9203 (online)