Aluminum Salen and Salan Polymerization Catalysts: From Monomer Scope to Macrostructure Control

Abstract

Tel +44 (0) 131 650 4726.Aluminum salen and salan complexes have been extensively employed as catalysts for the ring-opening polymerization of cyclic esters. The high tunability of the ligand framework has encouraged the systematic study of substituent effects on optimizing polymer and copolymer synthesis. Building on early work, designed catalysts are able to produce highly isotactic or heterotactic poly(lactic acid). The monomer scope has grown to include β-lactones, δ-valerolactone, lactide, (substituted) ε-caprolactones and macrolactones, with a significant level of control over molecular weight and dispersity (Đ). Polymer macrostructures have also been explored, often resulting in well-defined and predictable products. Macrostructures synthesized include random copolymers, AB diblock and ABA triblock copolymers and polymer stars.Polymer macrostructure control can tune properties not accessible through homopolymerization.

Aluminum Alkyl Complexes Bearing Salicylaldiminato Ligands: Versatile Initiators in the Ring-Opening Polymerization of Cyclic Esters

“…Recent literature reviews described the use of various aluminum complexes as polymerization catalysts [11][12][13]. This review focus on aluminum-based salicylaldiminato complexes and their reactivity in the ring-opening homo and copolymerization of commercially available and conventional lactones and lactides.…”

Green Polymer Chemistry: Some Recent Developments and Examples

“…Carbohydrate feedstock was engaged for the production of PLA (38)(39)(40)48), poly(2,5-dihydro-1,4-dioxane) (49), modified cellulose (50), and phosphorus -containing isosorbide esters (51).…”

“…Several chapters in this book deal with PLA (38)(39)(40)48). Enzymes and enzyme-based conjugates were proposed to be useful products for the treatment of wastewater (35).…”

Ring‐opening polymerization of (Macro)lactones by highly active mononuclear salen–aluminum complexes bearing cyclic β‐ketoiminato ligand

“…Among the various Al complexes, aluminum–salen complexes bearing salicylaldiminato moiety were found to be a versatile type of catalysts for ROP of both small ring‐sized lactones and macrolactone . Meanwhile, this type of catalyst showed a certain of stereocontrol ability in the ROP of racemic LA ( rac ‐LA), producing semicrystalline PLA from a mixture of L ‐LA and D ‐LA . The catalytic activity of salen–Al complex can be easily modulated by slightly varying substituent groups on ligand backbone.…”

“…9,[55][56][57][58][59] Meanwhile, this type of catalyst showed a certain of stereocontrol ability in the ROP of racemic LA (rac-LA), producing semicrystalline PLA from a mixture of L-LA and D-LA. 56,[60][61][62][63][64] The catalytic activity of salen-Al complex can be easily modulated by slightly varying substituent groups on ligand backbone. Nonetheless, most of the salicylaldiminato-based aluminum catalysts only exhibited relatively low efficiency.…”