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Reestructuración reversible de conjuntos de copolímero de bloque acuoso a través de cambios inducidos por estímulos
Anand Sundararaman1, Tim Stephan, Robert B Grubbs
1Department of Chemistry and Center for Nanomaterials Research, Dartmouth College, Hanover, New Hampshire 03755, USA.
Journal of the American Chemical Society
|August 30, 2008
Resumen
Los copolímeros de tribloque térmoresponsables forman estructuras distintas en el agua. Estos polímeros se autoensamblan en micelas a bajas temperaturas y vesículas a temperaturas más altas, con una transformación lenta y reversible.
Área de la Ciencia:
- La ciencia de los polímeros es la ciencia de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
- Química Física es la química física.
Sus antecedentes:
- Los copolímeros de tribloqueo ABC con secuencias de bloqueo específicas exhiben comportamientos únicos de autoensamblaje en soluciones acuosas.
- La temperatura de solución crítica inferior (LCST) del bloque termomorfo influye en la solubilidad y el estado de agregación del copolímero.
- Comprender estas transiciones estructurales dependientes de la temperatura es crucial para el diseño de materiales avanzados.
Objetivo del estudio:
- Para investigar el autoensamblaje de hidrófilos-termomórficos-hidrófobos ABC tribloqueo copolímeros en el agua.
- Para caracterizar los cambios estructurales inducidos por la temperatura de las micelas a las vesículas.
- Para determinar la reversibilidad y la cinética de la transición de fase observada.
Principales métodos:
- Síntesis y caracterización de un copolímero representativo de poli (óxido de etileno) -bloque-poli (N-isopropilacrilamida) -bloque-poliisopreno.
- Dispersión de luz dinámica y estática (DLS/SLS) para analizar el tamaño y la distribución de las micelas y las vesículas.
- Microscopía electrónica de transmisión (TEM) para la visualización directa de las nanoestructuras ensambladas.
Principales resultados:
- Copolímeros autoensamblados en distintas nanoestructuras dependiendo de la temperatura.
- Se observaron pequeñas micelas esféricas en soluciones acuosas por debajo del LCST del bloque termomórfico.
- Las vesículas grandes fueron favorecidas a temperaturas por encima del LCST, lo que indica un cambio estructural significativo.
- Se encontró que la transición de las micelas a las vesículas era reversible pero lenta, tardando varias semanas.
Conclusiones:
- Los copolímeros de tribloqueo ABC hidrófilo-termomórfico-hidrófobo pueden formar micelas y vesículas de forma reversible en el agua.
- El control de la temperatura por encima y por debajo del LCST del bloque termomorfo proporciona un mecanismo para ajustar la morfología de la nanoestructura.
- La cinética lenta de la transformación reversible sugiere aplicaciones potenciales donde se desean cambios estructurales controlados y graduales.
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