Issue 21, 2024

Stereoselective ring-opening polymerization of rac-lactide catalyzed by the proton sponge bisphosphazene 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene

Abstract

Synthesis of highly isotactic polylactide (PLA) via organocatalyzed stereoselective ring-opening polymerization (ROP) of racemic lactide (rac-LA) is a key strategy to improve the physico-chemical properties of PLA. In this context, the proton sponge bisphosphazene 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene (HMPN) was synthesized and applied to catalyze the stereoselective ROP of rac-LA. Semicrystalline PLA with a Pm of 0.75 was conveniently prepared at room temperature. PLAs with higher tacticity (Pm up to 0.93) and higher melting temperature (Tm up to 189 °C) were obtained at lowered temperature. Binary catalysts composed of HMPN and ureas exhibited both high activity (99% monomer conversion within 5 minutes) and high stereoselectivity (Pm up to 0.83) at room temperature. In situ NMR study of HMPN, urea, and BnOH demonstrated the weak interactions between HMPN and BnOH, verifying the kinetic inactivity to deprotonation of HMPN. Kinetic studies verified the controlled manner and chain end control mechanism for the HMPN/U-2 catalyzed ROP of rac-LA.

Graphical abstract: Stereoselective ring-opening polymerization of rac-lactide catalyzed by the proton sponge bisphosphazene 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene

Supplementary files

Article information

Article type
Paper
Submitted
03 Mar 2024
Accepted
09 May 2024
First published
10 May 2024

Polym. Chem., 2024,15, 2212-2219

Stereoselective ring-opening polymerization of rac-lactide catalyzed by the proton sponge bisphosphazene 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene

Z. Zhang, X. Guo, X. Kou, N. Zhao and Z. Li, Polym. Chem., 2024, 15, 2212 DOI: 10.1039/D4PY00242C

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