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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 28, Number 12
BKCSDE 28(12)
December 20, 2007

Title	Efficient Bimodal Ring-opening Polymerization of ε-Caprolactone Catalyzed by Titanium Complexes with N-Alkoxy-β-ketoiminate Ligands
Author	Min Ho Cho, Jin San Yoon, Ik-Mo Lee*
Keywords	N-Alkoxy-β-ketoiminate, Titanium complexes, ε-Caprolactone, Ring-opening polymerization, Transesterification
Abstract	A series of titanium complexes containing terdentate β-ketoiminate ligands were found to be efficient for the ring-opening polymerization of ε-caprolactone (ε-CL), producing poly(ε-caprolactone) (PCL) with bimodal distribution. Steric factors imposed by methyl substituents on the back bone of the alkoxy group affected significantly the polymerization rate and physical properties of the resulting PCL. Intra- and intermolecular transesterifications rather than disproportional rearrangements were responsible for the bimodal behavior and for the change in the molecular weight (M_w). Dilution with toluene reduced yield, and lowered polydispersity (PDI) and Mw of PCL, while the catalytic activities of the dimeric complex, [Ti(Oi-Pr)₂(N-alkoxy-β- ketoiminate)]₂ and Ti(Oi-Pr)₄ were not sensitive to the added solvent. The dimeric complex showed living character, while other catalysts suffered from chain termination reactions.
Page	2471 - 0
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