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Interacción entre la densidad de hidroxilo y las relajaciones en las membranas de poli (benciltrimetilamonio) - poli

Keti Vezzù^1,2, Ashley M Maes³, Federico Bertasi^1,4

¹Section of Chemistry for Technology, Department of Industrial Engineering, University of Padova, in Department of Chemical Sciences , Via Marzolo 1, I-35131 Padova, Italy.

Journal of the American Chemical Society

|January 10, 2018

Resumen

Se analizaron membranas de intercambio aniónico (AEM) con capacidades de intercambio iónico variables. Una transición clave afecta la conductividad iónica, con el agrupamiento que dificulta el transporte en membranas de mayor capacidad.

Área de la Ciencia:

Ciencia e ingeniería de polímeros
Ciencias de los materiales
La electroquímica

Sus antecedentes:

Las membranas de intercambio de aniones (AEM) son cruciales para aplicaciones electroquímicas como las pilas de combustible.
Comprender sus propiedades térmicas y eléctricas es vital para la optimización del rendimiento.
Los AEM basados en poli (vinilbenziltrimetilamonio) -b-poli (metilbutileno) ofrecen propiedades ajustables.

Objetivo del estudio:

Caracterizar exhaustivamente las MEA con diferentes capacidades de intercambio iónico (CEI).
Para aclarar la relación entre las transiciones térmicas, las propiedades eléctricas y la conductividad iónica.
Proponer un mecanismo de conductividad y comprender los factores que limitan el transporte aniónico.

Principales métodos:

Termogravimetría de alta resolución (HR-TGA)
Calorimetría de barrido diferencial modulada (mDSC)
Análisis mecánico dinámico (DMA)
Espectroscopía eléctrica de banda ancha

Principales resultados:

Se identificó una transición de cristal (Tg) y una transición de desorden a orden (Tδ) dependientes de IEC.
Respuesta eléctrica caracterizada, identificando las polarizaciones contribuyentes (σEP, σIP,1) y las relajaciones dieléctricas (β1, β2).
Se ha observado un reordenamiento del dipolo de los pares iónicos a Tδ (>20°C) que provoca una disminución significativa de la conductividad iónica; los impactos de agrupación afectan a las membranas superiores del IEC.

Conclusiones:

Se propone un mecanismo de doble vía de conducción (σEP y σIP,1) para los AEM.
La transición desorden-orden (Tδ) afecta significativamente la conductividad iónica al reordenar los dipolos.
El agrupamiento en membranas IEC altas impide el transporte aniónico eficiente, destacando un factor crítico para el diseño de AEM.

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