Physical vapor deposition as a route to hidden amorphous states.
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 T(g) (where T(g) 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 T(g), 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 T(g) -20 K, suggesting an underlying first-order liquid-to-liquid phase transition.
Dawson
Kevin J
KJ
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
Kearns
Kenneth L
KL
Yu
Lian
L
Steffen
Werner
W
Ediger
M D
MD
D007213:Indomethacin / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D044367:Phase Transition; D012542:Scattering, Radiation; D013696:Temperature; D014965:X-Rays
D007213:Indomethacin