TY - JOUR
T1 - Diffusion-controlled and "diffusionless" crystal growth near the glass transition temperature
T2 - Relation between liquid dynamics and growth kinetics of seven ROY polymorphs
AU - Sun, Ye
AU - Xi, Hanmi
AU - Ediger, M. D.
AU - Richert, Ranko
AU - Yu, Lian
N1 - Funding Information:
We thank the NSF-funded UW MRSEC and NSF (Grant No. DMR-0804786) for financial support. This work was supported in part by a fellowship from Merck Research Laboratories.
PY - 2009
Y1 - 2009
N2 - The liquid dynamics of 5-methyl-2-[(2-nitrophenyl)amino]-3- thiophenecarbonitrile, named ROY for its red, orange, and yellow crystal polymorphs, was characterized by dielectric spectroscopy and differential scanning calorimetry. Four of these polymorphs show fast " diffusionless" crystal growth at low temperatures while three others do not. ROY was found to be a typical fragile organic liquid. Its α relaxation process has time-temperature superposition symmetry across the viscous range (τα =100 s-100 ns) with the width of the relaxation peak characterized by a constant ΒKWW of 0.73. No secondary relaxation peak was observed, even with glasses made by fast quenching. For the polymorphs not showing fast crystal growth in the glassy state, the growth rate has a power-law relation with τα, u α τα-xi, where xi ≈0.7. For the polymorphs showing fast crystal growth in the glassy state, the growth is so fast near and below the glass transition temperature Tg that thousands of molecular layers can be added to the crystalline phase during one structural relaxation time of the liquid. In the glassy state, this mode of growth slows slightly over time. This slowdown is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the glass vapor pressure, or the rate of structural relaxation. This study demonstrates that from the same liquid or glass, the growth of some polymorphs is accurately described as being limited by the rate of structural relaxation or bulk diffusion, whereas the growth of other polymorphs is too fast to be under such control.
AB - The liquid dynamics of 5-methyl-2-[(2-nitrophenyl)amino]-3- thiophenecarbonitrile, named ROY for its red, orange, and yellow crystal polymorphs, was characterized by dielectric spectroscopy and differential scanning calorimetry. Four of these polymorphs show fast " diffusionless" crystal growth at low temperatures while three others do not. ROY was found to be a typical fragile organic liquid. Its α relaxation process has time-temperature superposition symmetry across the viscous range (τα =100 s-100 ns) with the width of the relaxation peak characterized by a constant ΒKWW of 0.73. No secondary relaxation peak was observed, even with glasses made by fast quenching. For the polymorphs not showing fast crystal growth in the glassy state, the growth rate has a power-law relation with τα, u α τα-xi, where xi ≈0.7. For the polymorphs showing fast crystal growth in the glassy state, the growth is so fast near and below the glass transition temperature Tg that thousands of molecular layers can be added to the crystalline phase during one structural relaxation time of the liquid. In the glassy state, this mode of growth slows slightly over time. This slowdown is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the glass vapor pressure, or the rate of structural relaxation. This study demonstrates that from the same liquid or glass, the growth of some polymorphs is accurately described as being limited by the rate of structural relaxation or bulk diffusion, whereas the growth of other polymorphs is too fast to be under such control.
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U2 - 10.1063/1.3200228
DO - 10.1063/1.3200228
M3 - Article
C2 - 19708750
AN - SCOPUS:69249171004
SN - 0021-9606
VL - 131
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 7
M1 - 074506
ER -