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Stable glasses of indomethacin and α,α,β-tris-naphthylbenzene transform into ordinary supercooled liquids
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10.1063/1.4768168
/content/aip/journal/jcp/137/20/10.1063/1.4768168
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/20/10.1063/1.4768168
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Figures

Image of FIG. 1.
FIG. 1.

d-IMC concentration profiles for a stable glass before and after annealing at 319 K (Tg + 4). The samples were prepared by vapor deposition at 265 K (0.85 Tg) and the total thickness of these samples was 800 ± 10 nm. The thick solid lines represent the experimental data. A growth front initiates at the free surface and propagates into the bulk (indicated by the arrow in the lower panel). The data are fitted with the 1D random walk model as described in the text (red exes). The diffusion coefficient for the liquid behind the growth front is determined to be D = 5.5 × 10−16 cm2/s, based on this fit. The thin red line indicates the calculated concentration profile using the previously reported value of D = 1.25 × 10−15 cm2/s.

Image of FIG. 2.
FIG. 2.

Self-diffusion coefficients as a function of temperature in IMC. The up-triangles show diffusion coefficients for the supercooled liquid (SCL) reported previously19 down-triangles indicate the SCL D values obtained here, and the solid symbols represent D values for the liquid behind the growth front obtained here. The solid line represents a temperature dependence of τα −0.76. The structural relaxation time τα was obtained from the dielectric relaxation data from Ref. 34. The inset shows the molecular structure of IMC.

Image of FIG. 3.
FIG. 3.

Self-diffusion coefficients as a function of temperature for the IMC liquid behind the growth front, as reported in Ref. 23 (open squares) and in this work (filled circles). The solid line represents the self-diffusion coefficients of the supercooled liquid from Figure 2. The dashed line is a vertically shifted version of the solid line.

Image of FIG. 4.
FIG. 4.

d-TNB concentration profile for a stable glass before and after annealing at 345 K (Tg - 2) for 196 500 s. The samples were prepared by vapor deposition at 295 K (0.85 Tg), with a total thickness of 750 ± 10 nm. The thick solid lines represent the experimental data. The lower panel shows evidence for a growth front that initiated at the free surface and propagated into the bulk up to the position indicated by the arrow. The data are fitted with the 1D random walk model, indicated by the red exes, and the resulting diffusion coefficient is 4.0 × 10−17 cm2/s. The thin red line indicates the calculated concentration profile using D = 1.1 × 10−16 cm2/s, the value reported in Ref. 23 for 345 K.

Image of FIG. 5.
FIG. 5.

Self-diffusion coefficients for TNB as a function of temperature for the supercooled liquid (open symbols) and the liquid produced by the transformation of a stable glass (filled circles, this work). Supercooled liquid data are represented by stars (field-gradient NMR, Ref. 45), up triangles (SIMS, Ref. 23), and down triangles (SIMS, this work). The solid line has the temperature dependence of η−0.87. The inset shows the molecular structure of TNB.

Image of FIG. 6.
FIG. 6.

Comparison of TNB self-diffusion coefficients as a function of temperature for the liquid produced by transforming a stable glass, as reported by Ref. 23 (open squares) and in this work (filled circles). The solid line shows the self-diffusion coefficients for the supercooled liquid (the same line shown in Figure 5). The dashed line is a vertically-shifted version of the solid line.

Image of FIG. 7.
FIG. 7.

Growth front velocities for stable glasses of IMC and TNB as a function of the supercooled liquid structural relaxation time. In each case, the temperature dependence of the growth front velocity is slightly weaker than the temperature dependence of τα.

Image of FIG. 8.
FIG. 8.

Growth front velocities for stable glasses of IMC and TNB as a function of the diffusion coefficient for the supercooled liquid. The diffusion coefficients obtained in Figures 2 (IMC) and 5 (TNB) were matched to the corresponding growth front velocity at the same temperature and plotted as shown here.

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/content/aip/journal/jcp/137/20/10.1063/1.4768168
2012-11-30
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Stable glasses of indomethacin and α,α,β-tris-naphthylbenzene transform into ordinary supercooled liquids
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/20/10.1063/1.4768168
10.1063/1.4768168
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