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La transición vítrea del agua, basada en experimentos de hiperquenchaje
V Velikov1, S Borick, C A Angell
1Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
Science (New York, N.Y.)
|December 18, 2001
Resumen
La temperatura de transición de vidrio (Tg) del agua se revisa a 165 K, resolviendo las discrepancias en estudios anteriores. Este hallazgo aclara el agua.
Área de la Ciencia:
- Química Física es la química física.
- Ciencia de los materiales Ciencia de los materiales.
- La termodinámica es la termodinámica.
Sus antecedentes:
- La temperatura de transición de vidrio (Tg) del agua sigue siendo un tema de debate, con valores experimentales contradictorios.
- Los vasos hipercalentados, incluida el agua, exhiben una exotermia de relajación de entalpía significativa al recalentarse.
- El análisis estándar de la relajación de entalpía en gafas típicamente implica escalar la temperatura exotérmica por Tg.
Objetivo del estudio:
- Para resolver la incertidumbre que rodea la temperatura de transición de vidrio (Tg) del agua hipercalentada.
- Para investigar el comportamiento calorimétrico del agua y compararlo con otros sistemas formadores de vidrio.
- Establecer un marco consistente para comprender la relajación de entalpía en vasos de agua.
Principales métodos:
- Calorimetría de barrido diferencial (DSC) para medir las exotermas de relajación de entalpía.
- Análisis de los datos calorimétricos mediante la escala de las temperaturas exotérmicas con la temperatura de transición de vidrio (Tg).
- Comparación del comportamiento del agua hipercalentada con otros conocidos formadores de vidrio y soluciones binarias.
Principales resultados:
- Usando el Tg comúnmente aceptado de 136 K, el agua hipercalentada muestra un comportamiento anómalo en comparación con otros vasos.
- El recálculo de Tg a 165 ± 5 K restaura el comportamiento normal del vidrio, alineando el agua con otros sistemas hipercalentados.
- Esta Tg revisada es consistente con los sistemas de redes anteriores como H2O, ZnCl2 y BeF2 en soluciones binarias.
Conclusiones:
- El Tg previamente aceptado de 136 K para el agua es probablemente incorrecto, lo que lleva a interpretaciones erróneas de su comportamiento de transición al vidrio.
- Un Tg revisado de 165 ± 5 K proporciona una comprensión consistente de la relajación de entalpía del agua, comparable con otros materiales formadores de vidrio.
- Este valor revisado es crucial para modelar con precisión las interacciones agua-biomolécula y comprender los sistemas biológicos.
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