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Title: Structures of glasses created by multiple kinetic arrests

X-ray scattering has been used to characterize glassy itraconazole (ITZ) prepared by cooling at different rates. Faster cooling produces ITZ glasses with lower (or zero) smectic order with more sinusoidal density modulation, larger molecular spacing, and shorter lateral correlation between the rod-like molecules. We find that each glass is characterized by not one, but two fictive temperatures Tf(the temperature at which a chosen order parameter is frozen in the equilibrium liquid). The higher Tfis associated with the regularity of smectic layers and lateral packing, while the lower Tfwith the molecular spacings between and within smectic layers. This indicates that different structural features are frozen on different timescales. The two timescales for ITZ correspond to its two relaxation modes observed by dielectric spectroscopy: the slower δ mode (end-over-end rotation) is associated with the freezing of the regularity of molecular packing and the faster α mode (rotation about the long axis) with the freezing of the spacing between molecules. Our finding suggests a way to selectively control the structural features of glasses.

 
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Award ID(s):
1904601 1720415
NSF-PAR ID:
10363215
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
American Institute of Physics
Date Published:
Journal Name:
The Journal of Chemical Physics
Volume:
156
Issue:
8
ISSN:
0021-9606
Page Range / eLocation ID:
Article No. 084504
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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