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Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions
Published on: March 21, 2014
Una nueva reacción de transferencia en cadena consecutiva a p-metilestireno e hidrógeno durante la polimerización de
1Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Journal of the American Chemical Society
|July 18, 2001
Resumen
Este estudio demuestra la transferencia de cadena consecutiva en la polimerización de propileno catalizado por metalloceno, lo que permite la síntesis de nuevos copolímeros de polipropileno diblock. Este método innovador transforma la catálisis del metalloceno en una polimerización aniónica viva.
Área de la Ciencia:
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- La catálisis de la catálisis.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los catalizadores de metaloceno son cruciales para la polimerización de las olefinas.
- El control del peso molecular y la arquitectura del polímero es un desafío clave.
- Es muy deseable desarrollar nuevos métodos para sintetizar copolímeros de bloque.
Objetivo del estudio:
- Informar sobre la primera instancia de transferencia de cadena consecutiva en la polimerización de propileno catalizado por metaloceno.
- Para explorar la síntesis de copolímeros de polipropileno diblock.
- Para investigar la influencia de los agentes de transferencia de cadena en la polimerización.
Principales métodos:
- Se utilizó un complejo metaloceno específico (rac-Me(2) Si[2-Me-4-Ph(Ind) ](2) ZrCl(2) / MAO) para la polimerización del propileno.
- Se introdujo p-metilestireno (o estireno) e hidrógeno como agentes de transferencia de cadena.
- Analizó la relación entre las proporciones de monómeros y el peso molecular del polímero.
- Investigó la metalización de unidades terminales de p-metilestireno para su posterior polimerización.
Principales resultados:
- Se logra la transferencia consecutiva de la cadena al p-metilestireno (o estireno) y luego al hidrógeno.
- El peso molecular del polímero mostró una proporción inversa a la relación molar de p-metilestireno/propileno y estireno/propileno.
- Las constantes de transferencia de la cadena se determinaron como k ((tr) / k ((p) = 1/6.36 y 1/7.5, respectivamente.
- El hidrógeno influyó en la actividad del catalizador pero no en el peso molecular del polímero.
- Copolímeros de dibloqueo de polipropileno preparados con éxito (por ejemplo, PP-b-PS) a través de la metalización y la polimerización aniónica viva.
Conclusiones:
- El método descrito ofrece una nueva vía para sintetizar los difíciles de preparar copolímeros de polipropileno diblock.
- El proceso efectivamente une la catálisis del metalloceno con la polimerización aniónica viva.
- Este trabajo amplía las posibilidades de crear arquitecturas poliméricas avanzadas.
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