Artículo
Ring-opening polymerization of ε-caprolactone by iodine charge-transfer complex
Fecha de publicación:
12/2002
Editorial:
John Wiley & Sons Inc
Revista:
Journal of Polymer Science Part B: Polymer Physics
ISSN:
0887-6266
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
The ring-opening polymerization of ε-caprolactone (ε-CL) catalyzed by iodine (I2) was studied. The formation of a charge-transfer complex (CTC) among triiodide, I3-, and ε-CL was confirmed with ultraviolet-visible spectroscopy. The monomer ε-CL was polymerized in bulk using I2 as a catalyst to form the polyester having apparent weight-average molecular weights of 85,900 and 45,500 at polymerization temperatures of 25 and 70 °C, respectively. The reactivity of both, ε-CL monomer and ε-CL:I2 CTC, was interpreted by means of the potential energy surfaces determined by semiempirical computations (MNDO-d). The results suggest that the formation of the ε-CL:I2 CTC leads to the ring opening of the ε-CL structure with the lactone protonation and the formation of a highly polarized polymerization precursor (ε-CL)+. The band gaps approximated from an extrapolation of the oligomeric polycaprolactone (PCL) structures were computed. With semiempirical quantum chemical calculations, geometries and charge distributions of the protonated polymerization precursor (ε-CL)+ were obtained. The calculated band gap (highest occupied molecular orbit/lowest unoccupied molecular orbit differences) agrees with the experiment. The analysis of the oligomeric PCL isosurfaces indicate the existence of a weakly lone pair character of the C=O and C - O bonds suggesting a ε-CL ring-opening specificity. © 2002 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys.
Palabras clave:
Catalysts
,
Charge Transfer
,
Polyesters
,
Ring-Opening Polymerization
Archivos asociados
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Identificadores
Colecciones
Articulos(INTEMA)
Articulos de INST.DE INV.EN CIENCIA Y TECNOL.MATERIALES (I)
Articulos de INST.DE INV.EN CIENCIA Y TECNOL.MATERIALES (I)
Citación
De Queiroz, Alvaro A. A.; Franca, Ecio J.; Abraham, Gustavo Abel; Román, Julio S.; Ring-opening polymerization of ε-caprolactone by iodine charge-transfer complex; John Wiley & Sons Inc; Journal of Polymer Science Part B: Polymer Physics; 40; 8; 12-2002; 714-722
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