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Una segunda transición de vidrio observada en líquidos homogéneos de un solo componente debido a la vitrificación
Ben A Russell1, Mario González-Jiménez1, Nikita V Tukachev1
1School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K.
Journal of the American Chemical Society
|November 18, 2023
Resumen
Los líquidos puros típicamente muestran una transición de vidrio. Sin embargo, los tetraalcoxidos de titanio exhiben dos, uno para propiedades a granel y otro para movimiento intramolecular, desafiando la comprensión convencional de las transiciones líquido-sólido.
Área de la Ciencia:
- Química Física
- Ciencias de los materiales
- Física de la materia condensada
Sus antecedentes:
- El súper enfriamiento de líquidos conduce a una transición de vidrio, formando un sólido amorfo con capacidad térmica reducida.
- Por lo general, se espera que los líquidos puros y homogéneos exhiban solo una transición de vidrio.
- Las transiciones de vidrio convencionales implican la detención dinámica de las propiedades del líquido a granel.
Objetivo del estudio:
- Para investigar el comportamiento de transición de vidrio de líquidos moleculares homogéneos de un solo componente.
- Determinar si pueden producirse múltiples transiciones de vidrio en dichos sistemas.
- Para aclarar la naturaleza de las distintas transiciones de vidrio observadas en los tetraalcoxidos de titanio.
Principales métodos:
- Se realizaron mediciones calorimétricas en una familia de tetraalcoxidos de titanio.
- El análisis se centró en la identificación y caracterización de cambios distintos en la capacidad térmica.
- El estudio correlacionó los eventos térmicos con la dinámica molecular y los cambios estructurales.
Principales resultados:
- Los tetraalcoxidos de titanio muestran dos transiciones de vidrio calorimétricas de magnitud comparable.
- Una transición corresponde a la detención dinámica de líquidos convencional.
- La segunda transición se atribuye a la congelación de los grados de libertad intramoleculares.
Conclusiones:
- Se observó un nuevo fenómeno de vitrificación intramolecular en líquidos moleculares homogéneos.
- Esto sugiere que los movimientos intramoleculares pueden sufrir una transición de vidrio independiente de las propiedades a granel.
- Los procesos de cruce de la barrera intramolecular no siempre pueden seguir el comportamiento de Arrhenius y pueden congelarse a temperaturas finitas.
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