High Molecular Weight Poly(α,α′,β-trisubstituted β-lactones) As Generated by Metal-Free Phosphazene Catalysts.

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• 作者：Julien De Winter ; Olivier Coulembier ; Pascal Gerbaux ; Philippe Dubois
• 刊名：Macromolecules
• 出版年：2010
• 出版时间：December 28, 2010
• 年：2010
• 卷：43
• 期：24
• 页码：10291-10296
• 全文大小：875K
• 年卷期：v.43,no.24(December 28, 2010)
• ISSN：1520-5835

文摘

The use of different phosphazene bases has been investigated as catalysts in polymerization of [R,S]-4-benzyloxycarbonyl-3,3-dimethyl-2-oxetanone (dMMLABz) in presence of carboxylic acids used as initiators. Whatever the catalyst considered (P₁-t-Bu, P₂-t-Bu, or P₄-t-Bu) a very good control over the polymerization has been obtained in terms of polyester molecular weights and end-groups fidelity as attested by spectroscopic techniques such as ¹H NMR, gel permeation chromatography (GPC) and matrix assisted laser desorption ionization-mass spectrometry (MALDI−MS) experiments. Characterized by a complete absence of transfer reactions, the system allows for the generation of very high molecular weight PdMMLABz trough a mechanism selectively involving the “O-alkyl” scission of the β-lactone monomer. A clear dependence of the basicity of the phosphazene catalyst on the overall polymerization kinetics has been observed where the most basic catalytic species, i.e., 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranyl-idenamino]-2Λ⁵,4Λ⁵-catenadi(phosphazene) (P₄-t-Bu), shows the highest active ion-pair. Accordingly, P₄-t-Bu allowed for the synthesis of PdMMLABz chains characterized by a number-average molecular weight higher than 1.5 × 10⁶ g mol⁻¹.