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Updated: Jun 13, 2026

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance
Published on: September 5, 2018
Fast surface crystallization of amorphous griseofulvin below T g
Lei Zhu1, Janan Jona, Karthik Nagapudi
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Purpose:
To study crystal growth rates of amorphous griseofulvin (GSF) below its glass transition temperature (T (g)) and the effect of surface crystallization on the overall crystallization kinetics of amorphous GSF.
Methods:
Amorphous GSF was generated by melt quenching. Surface and bulk crystal growth rates were determined using polarized light microscope. X-ray powder diffraction (XRPD) and Raman microscopy were used to identify the polymorph of the crystals. Crystallization kinetics of amorphous GSF powder stored at 40 degrees C (T (g)-48 degrees C) and room temperature (T (g)-66 degrees C) was monitored using XRPD.
Results:
Crystal growth at the surface of amorphous GSF is 10- to 100-fold faster than that in the bulk. The surface crystal growth can be suppressed by an ultrathin gold coating. Below T (g), the crystallization of amorphous GSF powder was biphasic with a rapid initial crystallization stage dominated by the surface crystallization and a slow or suspended late stage controlled by the bulk crystallization.
Conclusions:
GSF exhibits the fastest surface crystallization kinetics among the known amorphous pharmaceutical solids. Well below T (g), surface crystallization dominated the overall crystallization kinetics of amorphous GSF powder. Thus, surface crystallization should be distinguished from bulk crystallization in studying, modeling and controlling the crystallization of amorphous solids.
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