Ring-opening polymerization by lithium catalysts: an overview

Abstract

This critical review summarizes recent developments in the preparation and application of lithium catalysts/initiators such as, alkyl lithium, alkoxy lithium and bimetallic lithium compounds for ring-opening polymerization (ROP). The ROP of cyclic esters, cyclic carbonates, cyclo-silazanes, cyclo-silanes, cyclo-siloxanes, cyclo-carboxylate, cyclic phosphirene and quinodimethanes are covered in this review. The present paper emphasizes the polymerization kinetics and the control exhibited by the different types of lithium initiators/catalysts. For the cases where useful properties, such as high molecular weight, narrow PDI, or stereocontrol, have been observed, a more detailed examination of the mechanistic studies of the catalysts/initiators are provided. Furthermore, this review also focuses on the synthesis of block copolymers and graft copolymers by ROP principle. The topics covered in this review regarding lithium compounds toward ROP will be of interest to inorganic, organic and organometallic chemists, material, polymer and catalytic scientists due to its unique mode of activation as compared to transition and inner transition-metals. In addition, use of these compounds in catalysis is steadily growing, because of the complementary reactivity toward ROP as compared to other metals. Finally, some aspects and opportunities which may be of interest in the future are suggested (143 references).

Schiff Base Transition Metal Complexes for ROP of L-Lactide

“…On the basis of the "immortal" property of lactide polymerization demonstrated by several metal complexes [1] and the evidence of in situ formation of metal alkoxide in the presence of alcohol, the complex M-HMBBD was expected to behave as catalysts towards the ROP of lactide in the presence of benzyl alcohol. The M-HMBBD in presence of benzyl alcohol does initiate the ring-opening polymerization of L-lactide (LA) in dichloromethane at 30 o C (Scheme 3).…”

“…Poly(lactic acid) (PLA) [1], produced by the ring-opening polymerization (ROP) of lactide (LA), is a leading biodegradable and biocompatible polyester and their degradation into nontoxic components (water and carbon dioxide) make polylactides (PLAs) very useful for its biomedical and pharmaceutical applications such as controlled drug delivery systems. [2], [3] Owing to their mechanical properties, PLAs are widely used in surgery as sutures, orthopedic applications, tissue engineering and biodegradable internal fixation devices for repair of fractures to small bones and joints [4].…”

Lactide polymerization with iron alkoxide complexes

“…7 In most cases, if not all, bis(imino) pyridine metal complexes are produced through simple coordination reactions, whereby the corresponding metal salts are introduced in solution with the ligand. The following scheme presents a general representation of such a coordination and complexation reaction.…”

Synthesis and Structural Studies of Nickel Complex Supported by-ONNO-Tetra Dentate Schiff-Base Ligand: Efficient Catalysts for Oxidation of Phenol

“…The amount of 3-MHBdMBn Schiff base anchored on polymer beads and its composition were estimated using Haraeus Carlo Ebra 1108 Elemental Analyzer. The 1 H-NMR spectra of 3-MHBdMBn Schiff base and nickel complex were recorded on an FT-NMR-Brucker 300 MHz Spectrometer using DMSO-d 6 as a solvent and tetramethylsilane (TMS) as an internal reference. The magnetic moment (µ) of nickel complex was measured using Vibrating Sample Magnetometer-155.…”

“…The supported catalysts are easily recovered without any substantial loss in their catalytic activity [1][2] but homogeneous catalysts are not recovered easily. The Schiff base complexes of transition metal ions shown high catalytic activities in various chemical reactions such as epoxidation of olefins, [3] oxidation, [4][5] and polymerization of ethylene, [6][7] but polymer-supported metal complexes showed high catalytic activity [4,5,[8][9][10], in comparison to homogeneous catalysts. The manganese(II) salen complexes anchored on tailor-made polymers were more enantioselective without any mass transfer limitation for alkenes on polymer supports.…”