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Conocimientos computacionales sobre los desafíos para polimerizar monómeros polares
Dean M Philipp1, Richard P Muller, William A Goddard
1Materials and Process Simulation Center (139-74), California Institute of Technology, Pasadena 91125, USA.
Journal of the American Chemical Society
|August 22, 2002
Resumen
Este estudio utilizó métodos computacionales para explorar cómo los catalizadores de paladio polimerizan los monómeros polares. Los resultados muestran que se favorece una vía de inserción específica, lo que pone de relieve los desafíos en el diseño de catalizadores de polimerización efectivos.
Área de la Ciencia:
- Química computacional es la química computacional.
- La ciencia de los polímeros es la ciencia de los polímeros.
- La catálisis de la catálisis.
Sus antecedentes:
- La polimerización de monómeros polares sigue siendo un desafío significativo en la química sintética.
- Los catalizadores de paladio (Pd) son ampliamente utilizados, pero tienen dificultades para incorporar grupos funcionales polares en las cadenas de polímeros.
- Comprender los pasos fundamentales de la polimerización es crucial para el diseño del catalizador.
Objetivo del estudio:
- Para investigar los mecanismos de propagación en cadena para la polimerización de monómeros polares utilizando catalizadores de di-imine de paladio.
- Para identificar las vías de inserción preferidas y las estructuras intermedias durante la polimerización.
- Aclarar los desafíos clave en el desarrollo de catalizadores para la polimerización de monómeros polares.
Principales métodos:
- Los primeros principios de los cálculos de la teoría funcional de la densidad (DFT), específicamente el nivel B3LYP/6-31G de la teoría.
- Investigación de la inserción de etileno en enlaces Pd-C con cuatro monómeros polares: acrilato de metilo, acetato de vinilo, cloruro de vinilo y acrilonitrilo.
- Optimización de la estructura de los intermedios y estados de transición utilizando un modelo dieléctrico continuo para los efectos de solvación.
Principales resultados:
- La vía de inserción 2,1 fue favorecida consistentemente para los cuatro monómeros polares, de 3 a 5 kcal/mol.
- Esta vía favorecida conduce a fuertes interacciones entre el grupo polar y la creciente cadena de polímero / centro metálico.
- También se analizaron las inserciones posteriores de monómeros polares o etileno, revelando complejas estructuras intermedias.
Conclusiones:
- La preferencia de inserción 2,1 y las fuertes interacciones entre grupos polares y metales presentan dificultades inherentes para el diseño del catalizador.
- Las ideas computacionales señalan obstáculos críticos para lograr la polimerización controlada de los monómeros polares.
- Se necesita un mayor desarrollo de catalizadores para abordar estos desafíos mecanicistas fundamentales.
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