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Acoplamiento de óxido de propileno y lactida en un centro de porfirina cromo (III)

Vagulejan Balasanthiran¹, Chandrani Chatterjee, Malcolm H Chisholm

¹Department of Chemistry and Biochemistry, The Ohio State University , 100 West 18th Avenue, Columbus, Ohio 43210, United States.

Journal of the American Chemical Society

|January 29, 2015

Resumen

5,10,15,20-Cloruro de cromo de tetrafenilporfirina (TPPCrCl) y PPN ((+) Cl ((-) polimerizan selectivamente el lactido hasta convertirlo en polilactido. La estereoselectividad es dependiente de la temperatura, con bajas temperaturas que producen polímeros altamente isotácticos y temperaturas más altas que conducen a reacciones secundarias.

Área de la Ciencia:

Química de Polímeros La Química de Polímeros es la química de los polímeros.
La catálisis por catálisis.
Síntesis orgánica La síntesis orgánica.

Sus antecedentes:

El polilactido (PLA) es un polímero biodegradable con diversas aplicaciones.
La polimerización controlada del lactido es crucial para adaptar las propiedades del PLA.
La polimerización estereoselectiva influye en las características físicas y de degradación del PLA.

Objetivo del estudio:

Para investigar la polimerización estereoselectiva del lactido mediante el uso de cloruro de cromo de tetrafenilporfirina 5,10,15,20 (TPPCrCl) y PPN(+) Cl(-).
Para determinar el efecto de la temperatura en la selectividad de la polimerización y las reacciones secundarias.
Explorar el mecanismo de formación de PLA y sus potenciales subproductos.

Principales métodos:

La polimerización de apertura de anillo de lactido (L- y rac-LA) iniciada por TPPCrCl/PPN(+) Cl(-).
La polimerización se lleva a cabo en un solvente puro de óxido de propileno (PO) a varias temperaturas (0 °C, 25 °C, 60 °C +).
Análisis de la estereoquímica del polímero (isotacticidad) y de la formación de subproductos.

Principales resultados:

TPPCrCl/PPN(+)Cl(-) polimeriza eficientemente el lactido a PLA con un grupo final específico (-OCHMeCH2Cl).
A 0 °C y por debajo, la polimerización racémica de lactida produce PLA altamente isotáctico (enriquecido en iii tetras).
Las temperaturas más altas (25 °C+) reducen la estereoselectividad debido a la significativa transesterificación y encadenamiento de PO, formando 3,6-dimetil-1,4-dioxan-2-ona.

Conclusiones:

TPPCrCl/PPN(+)Cl(-) es un sistema catalizador eficaz para la polimerización estereoselectiva de lactida.
El control de la temperatura es crítico para lograr una alta isotacticidad en la síntesis de PLA.
Comprender las reacciones secundarias como la encadenamiento de PO es importante para optimizar la producción y las propiedades de PLA.

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