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Modelado de la ramificación aleatoria del metilo en copolímeros de etileno/propileno utilizando química de la
John C Sworen1, Jason A Smith, Kenneth B Wagener
1The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
Journal of the American Chemical Society
|February 20, 2003
Resumen
Los investigadores modelaron aleatoriamente copolímeros de etileno/propileno (EP) utilizando la polimerización por metástasis de dieno acíclico (ADMET). Observaron una fase hexagonal en los copolímeros EP de alto etileno y encontraron que el punto de fusión disminuye con el aumento de la ramificación.
Área de la Ciencia:
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los copolímeros de etileno/propileno (EP) son ampliamente utilizados, pero sus relaciones estructura-propiedad precisas son complejas.
- Comprender la influencia de la ramificación en la estructura del copolímero y las propiedades térmicas es crucial para el diseño de materiales.
Objetivo del estudio:
- Para modelar y sintetizar copolímeros aleatorios de etileno/propileno (EP) con ramificación controlada utilizando la polimerización por metástasis de dieno acíclico (ADMET).
- Caracterizar las estructuras primarias y de nivel superior de estos copolímeros.
- Para investigar el comportamiento térmico y las transiciones de fase en relación con el contenido de la rama.
Principales métodos:
- Síntesis de seis copolímeros EP modelo a través de la polimerización ADMET.
- Caracterización mediante resonancia magnética nuclear (RMN), espectroscopia infrarroja (IR), calorimetría de barrido diferencial (DSC), difracción de rayos X de ángulo ancho (WAXD) y cromatografía por permeación de gel (GPC).
- Análisis de las características estructurales, comportamiento de fase y propiedades térmicas.
Principales resultados:
- Se sintetizaron con éxito copolímeros EP con contenido variable de rama de metilo (de 1,5 a 55,6 por 1000 carbonos).
- La primera observación de una fase hexagonal en copolímeros EP con alto contenido de etileno (90%) sin manipulación externa.
- Se observó una disminución en el punto de fusión y el calor de fusión con el aumento del contenido de ramas.
Conclusiones:
- La polimerización ADMET proporciona una ruta para modelar copolímeros EP aleatorios con ramificación controlada.
- Los copolímeros EP con alto contenido de etileno pueden exhibir una formación de fase hexagonal intrínseca.
- La ramificación tiene un impacto significativo en las propiedades térmicas y el comportamiento cristalino de los copolímeros EP.
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