Physical vapor deposition as a route to hidden amorphous states
- aDepartment of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706;
- bSchool of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705; and
- cMax Planck Institute for Polymer Research, Postfach 3148, 55128 Mainz, Germany
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Edited by Frank H. Stillinger, Princeton University, Princeton, NJ, and approved June 24, 2009 (received for review February 9, 2009)
Abstract
Stable glasses of indomethacin (IMC) were prepared by using physical vapor deposition. Wide-angle X-ray scattering measurements were performed to characterize the average local structure. IMC glasses prepared at a substrate temperature of 0.84 Tg (where Tg is the glass transition temperature) and a deposition rate of 0.2 nm/s show a broad, high-intensity peak at low q values that is not present in the supercooled liquid or melt-quenched glasses. When annealed slightly above Tg, the new WAXS pattern transforms into the melt-quenched glass pattern, but only after very long annealing times. For a series of samples prepared at the lowest deposition rate, the new local packing arrangement is present only for deposition temperatures below Tg −20 K, suggesting an underlying first-order liquid-to-liquid phase transition.
Footnotes
- 1To whom correspondence should be addressed. E-mail: ediger{at}chem.wisc.edu
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Author contributions: M.D.E. designed research; K.J.D., K.L.K., and W.S. performed research; L.Y. contributed new reagents/analytic tools; K.J.D., L.Y., W.S., and M.D.E. analyzed data; and K.J.D. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
