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Comprender la polimerización radical por transferencia atómica: efecto de las estructuras de ligando e iniciador en
Wei Tang1, Yungwan Kwak, Wade Braunecker
1Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Journal of the American Chemical Society
|July 23, 2008
Resumen
Este estudio cuantifica las constantes de equilibrio para la polimerización radical de transferencia atómica catalizada por cobre (ATRP), revelando fuertes dependencias en las estructuras de ligando e iniciador. Estos hallazgos son cruciales para controlar los procesos de polimerización.
Área de la Ciencia:
- Química de Polímeros La química de los polímeros es la química de los polímeros.
- Síntesis orgánica La síntesis orgánica.
- La catálisis es la catálisis.
Sus antecedentes:
- La polimerización radical por transferencia atómica (ATRP) es una técnica de polimerización controlada.
- Los catalizadores a base de cobre son ampliamente utilizados en el ATRP.
- Comprender las constantes de equilibrio es vital para el diseño del catalizador y el control de la reacción.
Objetivo del estudio:
- Determinar sistemáticamente las constantes de equilibrio para el ATRP basado en cobre.
- Para investigar la influencia de la estructura de ligando e iniciador en el equilibrio de ATRP.
- Para establecer relaciones estructura-actividad para los complejos Cu (I) /ligando.
Principales métodos:
- Determinación de las constantes de equilibrio en acetonitrilo a 22°C.
- Variación sistemática de los ligandos (bidentado, tridentado, tetradentado, trípodo, puenteado) y los iniciadores (alquilo haluros terciarios y primarios).
- Extrapolación de las constantes de equilibrio no medibles utilizando datos de referencia.
Principales resultados:
- Las constantes de equilibrio abarcan más de 7 órdenes de magnitud.
- La denticidad del ligando tiene un impacto significativo en la actividad: tetradentato > tridentato > bidentato.
- Los ligandos trípodos y puentes muestran una mayor actividad que sus contrapartes lineales.
- Los haluros de alquilo terciarios y los bromuros de alquilo exhiben mayores constantes de equilibrio.
- Los derivados de nitrilo son los más activos, seguidos por los derivados de bencilo y éster.
- Se observaron fuertes correlaciones entre las constantes de equilibrio, los potenciales redox Cu (II/I) y las energías de disociación de los enlaces C-X.
Conclusiones:
- La estructura del ligando y el iniciador son determinantes críticos del equilibrio del ATRP basado en Cu.
- El diseño del catalizador se puede optimizar seleccionando los ligandos e iniciadores apropiados.
- Los potenciales redox y las energías de disociación de enlaces son predictores confiables de la actividad de ATRP.
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