Review – recent development of ring-opening polymerization of cyclic esters using aluminum complexes

Abstract

With the development of the technology of ring-opening polymerization (ROP) rapidly, many novel aluminum complexes have been designed, synthesized, and applied in initiating ROP of cyclic esters and new stereoregular polymerization mechanism of lactide polymerization have been reported. In this review, the mechanism for ROP of cyclic ester, synthesis of aluminum complexes containing tetradendete ligand, tridentate ligand, bidentate ligand, and bimetallic complexes containing aluminum were reviewed. We hope to give some helpful information for designing aluminum complexes, improving activity, and stereoregularity of aluminum complexes.Keywords: ring-opening polymerization; cyclic ester; aluminum complexes; stereoregularity IntroductionAliphatic polyester is biodegradable and biocompatible materials, which prepared using ring-opening polymerization (ROP) of cyclic ester such as lactide, caprolactone. trimethylene carbonate, and other cyclic ester. [1,2] Due to effective influences of microstructure, molecular weight, and polydispersity indexes (PDIs) on polyester physicochemical properties, the controlled/living ROP for synthesis of polyester which enables the ready to control these parameters attracted an extraordinary amount of research recently.[3-6] During the last two decades, the improvement in catalyst makes it possible to design and synthesis of polyester. [7][8][9][10]

Tuning thermal properties and microphase separation in aliphatic polyester ABA copolymers

“…[1][2][3][4] Ring-opening polymerisation (ROP) of the corresponding cyclic esters, catalysed by either an organocatalyst or a metal complex, has been investigated for improved control over the polymer properties by affording polymers with predictable molecular weight and low dispersity while minimising chain transfer and termination reactions. [8][9][10][11] To grow this range of polymers, aliphatic polyester copolymers have been explored. However, due to the vast majority of reports focusing on a limited number of monomers, namely lactide, glycolide and ε-caprolactone, the range of accessible materials is also quite limited.…”

Mechanistic Insight into the Stereochemical Control of Lactide Polymerization by Salan–Aluminum Catalysts

“…[1,2] PLA is generally produced by the catalyzed ring-opening polymerization (ROP) of its cyclic dilactone lactide (LA). [3] TheR OP by metal-based catalysts [4,5] typically propagates by an insertion of the lactide carbonyl group to ametal À alkoxo group,followed by breaking of the bond between the acyl carbon atom and the endocyclic oxygen atom to form an ew metalÀalkoxo bond. Thes tereogenic centers of lactide are not affected by this process,s op olymerization of the homochiral l-LA or d-LA can only lead to isotactic PLA.…”

Lactide polymerization with iron alkoxide complexes

“…9 Others, such as Chirik and coworkers, went further, actually making use of "the ability of bis(imino) pyridines to serve as electron reservoirs," thereby "designing new catalysts or reagents for small molecule activation." 7 Prior studies had already pointed out and demonstrated how such bis(imino) pyridine ligands are not only redox active ligands that can accept up to three electrons in the antibonding orbitals of their conjugated π-system, 12 but also even chemically active molecules during metal-based catalytic reactions, 13 where certain alkylating agents may attack not only the imino moity of the ligand framework, but even the carbon and nitrogen atoms on the pyridine ring. Indeed, Enright et al went even further in their analysis of the oxido-reductive properties of bis(imino) pyridine ligands and explained how "the ability of the large π-system to accommodate negative charge might concurrently lead to increased Lewis acidity of the metal center, which has an obvious positive impact on catalytic performance."…”

“…1,[5][6][7][8][9][10][11] Catalysts based on group 13 elements Al, Ga, and In often display low activities, but these systems have attracted interest thanks to their often high isoselectivity. 8,[12][13][14] With regard to late-transition-metal catalysts, the seminal work of Coates and coworkers 15 has led to extensive investigation of zinc complexes. 5 Recent reports from the Schaper group have also introduced several highly active catalysts based on Cu.…”