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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Nanoconfinement Effects on the Glass Transition and Crystallization Behaviors of Nifedipine
Sixue Cheng1, Gregory B McKenna1
1Department of Chemical Engineering, Whitacre College of Engineering , Texas Tech University , Lubbock , Texas 79409-3121 , United States.
Abstract:
The impact of nanoconfinement on the crystallization and glass transition behaviors of nifedipine (NIF) has been investigated using differential scanning calorimetry. Nanoconfinement was provided by imbibing the NIF into a porous medium (controlled pore glass, CPG), and results were compared with the unconfined bulk material. Consistent with previous results from the literature, both glass transition temperature Tg and melting temperature Tm decrease with decreasing pore size. The melting temperature was found to decrease with the reciprocal of pore diameter and could be analyzed with the Gibbs-Thomson equation. In addition, for confinement sizes of 7.5 and 12 nm, it was found that no cold-crystallization occurs upon heating from the glassy state to above the expected melting transition. Finally, at intermediate confinements we find evidence of a possible new, confinement-induced polymorph of NIF.
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