Work

Tridentate [ONN] Iminophenolate Aluminum Complexes for Controlled Ring-Opening (Co)Polymerization of rac -Lactide, ε-Caprolactone, and δ-Valerolactone: Impact of Pendant Diamine Donor Arms and Ligand Substituents on Catalytic Performance

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide A series of tridentate [ONN] iminophenolate aluminum complexes ( 1 – 15 ) bearing hemilabile pendant diamine donor arms with tunable flexibility and systematically varied phenoxy substituents was successfully synthesized and structurally characterized in solution. All complexes promoted the controlled/living ring-opening polymerization of rac -lactide ( rac -LA), ε-caprolactone (ε-CL), and δ-valerolactone (δ-VL) in the presence of benzyl alcohol, affording polyesters with good control over molar mass and dispersity. Lewis acidity studies of representative complexes 1, 6, and 11, featuring ethylenedimethylamine, propylenedimethylamine, and 2,2-dimethylpropanedimethylamine donor arms, respectively, provided insights into the relationship between the accessibility of the metal center and catalytic performance. The accessibility of the aluminum center increased in the order 1 < 6 < 11, paralleling the enhancement in catalytic activity and establishing the flexibility of the pendant donor arm as a key structural parameter for improving the performance of aluminum complexes. Taking advantage of the controlled nature of these polymerizations, well-defined diblock copolymers, including poly(CL- b - rac- LA), poly(VL- b - rac -LA), poly(CL- b -VL), and poly(VL- b -CL), were successfully synthesized via sequential-feed copolymerization. In addition, single-feed copolymerization of ε-CL and δ-VL afforded the perfect random poly(CL- co -VL), with average caproyl and valeroyl sequence lengths ( L CL and L VL ) close to 2. These results establish hemilabile flexible pendant donor arms and phenoxy substituents as effective design elements for tuning tridentate aluminum catalysts in the controlled polymerization of cyclic esters.

Source: Macromolecules

DOI: 10.1021/acs.macromol.6c01180

Authors: Kunanon Jampakaew, Wasan Joopor, Pimpa Hormnirun

Institution: Kasetsart University

Language: English

Topic: biodegradable polymer synthesis and properties

Subfield: Biomaterials

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: Office of the Higher Education Commission, Kasetsart University Research and Development Institute, Graduate School, Kasetsart University, Center of Excellence for Innovation in Chemistry