High-Pressure Crystallization of Glass-Forming Liquids …
51
3 Summary and Conclusion
Controlling crystallization and glass-formation is important from both fundamental
and practical application points of view. Crystallization is commonly discussed in
many different fields of science, e.g., physics, chemistry, pharmacy, or material engineering. Irrespectively of that, there are still many numerous unclear aspects related
to the crystallization process. Here, we demonstrate that some of them cannot be
simply addressed by operating only with one thermodynamic variable, temperature,
or either pressure. We need both, inasmuch the phase diagram for each substance
is two, not one dimensional. Therefore, by ably control temperature and pressure
conditions or moving in T-p phase space along certain iso-lines it is possible to
affect the crystallization outcome in a fully aware manner. This has allowed us
to perform first experimental attempts aimed at controlling the kinetic and thermodynamic factors responsible for crystallization progress, and demonstrate that
the crystallization tendency of the glass-forming liquids is a path-dependent, and
can be tuned—just like with the temperature—by changing the rate of compression/decompression. Another interesting aspect gained from this study is the peculiar
behavior of racemic compounds, which in contrast to other systems shows spectacular slowing down of the crystallization progress on increased pressure. This raises
the question of the possibility of spontaneous separation of enantiomers/or changes
in the enantiomeric concentration as the effect of high-pressure crystallization. More
research on high-pressure crystallization of glass-formers with different structures
and intermolecular interactions; particularly liquids with competing interactions and
strong directional bonding (e.g., hydrogen bonds and ionic liquids) should elucidate
whether our observation regarding crystallization behavior of glass-forming liquids
along different iso-lines can be treated as more general. This should benefit in the
future to more ably control crystallization propensity of glass-forming liquids under
various thermodynamic conditions.
Acknowledgements KA is grateful for the financial support from the National Science Centre
within the framework of the SONATA BIS project (Grant No. 2017/26/E/ST3/00077).
References
1. Ediger MD, Harrowell P (2012) Perspective: supercooled liquids and glasses. J Chem Phys
137:080901
2. Kawasaki T, Tanaka H (2010) Formation of a crystal nucleus from liquid. PNAS
107(32):14036–14041
3. Tammann G (1925) Glasses as supercooled Liquids. J Soc Glas Technol 9:166–185
4. Pukánszky B, Mudra I, Staniek P (2004) Relation of crystalline structure and mechanical
properties of nucleated polypropylene. J Vinyl Addit Technol 3(1):53–57
5. Myerson A (2001) Handbook of industrial crystallization, 2nd edn. Butterworth-Heinemann
6. Wunderlich B (1973) Macromolecular physics. Volume 1: Crystal structure, morphology,
defects. Academic Press
51
3 Summary and Conclusion
Controlling crystallization and glass-formation is important from both fundamental
and practical application points of view. Crystallization is commonly discussed in
many different fields of science, e.g., physics, chemistry, pharmacy, or material engineering. Irrespectively of that, there are still many numerous unclear aspects related
to the crystallization process. Here, we demonstrate that some of them cannot be
simply addressed by operating only with one thermodynamic variable, temperature,
or either pressure. We need both, inasmuch the phase diagram for each substance
is two, not one dimensional. Therefore, by ably control temperature and pressure
conditions or moving in T-p phase space along certain iso-lines it is possible to
affect the crystallization outcome in a fully aware manner. This has allowed us
to perform first experimental attempts aimed at controlling the kinetic and thermodynamic factors responsible for crystallization progress, and demonstrate that
the crystallization tendency of the glass-forming liquids is a path-dependent, and
can be tuned—just like with the temperature—by changing the rate of compression/decompression. Another interesting aspect gained from this study is the peculiar
behavior of racemic compounds, which in contrast to other systems shows spectacular slowing down of the crystallization progress on increased pressure. This raises
the question of the possibility of spontaneous separation of enantiomers/or changes
in the enantiomeric concentration as the effect of high-pressure crystallization. More
research on high-pressure crystallization of glass-formers with different structures
and intermolecular interactions; particularly liquids with competing interactions and
strong directional bonding (e.g., hydrogen bonds and ionic liquids) should elucidate
whether our observation regarding crystallization behavior of glass-forming liquids
along different iso-lines can be treated as more general. This should benefit in the
future to more ably control crystallization propensity of glass-forming liquids under
various thermodynamic conditions.
Acknowledgements KA is grateful for the financial support from the National Science Centre
within the framework of the SONATA BIS project (Grant No. 2017/26/E/ST3/00077).
References
1. Ediger MD, Harrowell P (2012) Perspective: supercooled liquids and glasses. J Chem Phys
137:080901
2. Kawasaki T, Tanaka H (2010) Formation of a crystal nucleus from liquid. PNAS
107(32):14036–14041
3. Tammann G (1925) Glasses as supercooled Liquids. J Soc Glas Technol 9:166–185
4. Pukánszky B, Mudra I, Staniek P (2004) Relation of crystalline structure and mechanical
properties of nucleated polypropylene. J Vinyl Addit Technol 3(1):53–57
5. Myerson A (2001) Handbook of industrial crystallization, 2nd edn. Butterworth-Heinemann
6. Wunderlich B (1973) Macromolecular physics. Volume 1: Crystal structure, morphology,
defects. Academic Press