Alkali and Alkaline Earth Metal Complexes as Versatile Catalysts for Ring‐Opening Polymerization of Cyclic Esters

Abstract

Biodegradable polyesters such as poly(ϵ‐caprolactone) (PCL) and poly(lactic acid) (PLA) have been considered for use in several areas, such as drug delivery devices, sutures, tissue engineering, and GBR membranes, due to its bio‐renewability, biodegradability, and biocompatibility. Several synthetic techniques for the preparation of polyesters have been reported in the literature, amongst which the ring‐opening polymerization (ROP) of cyclic esters is the most efficient. A convenient approach to access iso‐selective PLAs is polymerization of racemic lactide (rac‐LA), which shows excellent stereoregularity without the need for costly chiral auxiliaries or ligands. In this personal account, we review a series of methods that have been practiced to the synthesis of biodegradable polyesters from various cyclic monomers using alkali and alkaline earth metal complexes as efficient catalysts.

Recent Advances in Engineering Bioinks for 3D Bioprinting

“…PCL is a high‐molecular‐weight organic polymer formed from the ε‐caprolactone monomer after ring‐opening polymerization. [ 134 ] PCL is used in tissue engineering owing to its desirable mechanical characteristics, degradability, and low cost. [ 135 ] For example, oxalate (OX)‐linked oligocaprolactone multi‐block copolymer (PCL‐OX) can be used to synthesize a rapidly degradable hydrogel for drug delivery.…”

Three-Dimensional Printing Strategies for Irregularly Shaped Cartilage Tissue Engineering: Current State and Challenges

“…PCL is a polymer obtained by ring-opening polymerization of ε-caprolactone monomers ( Bhattacharjee et al, 2021 ). The compressive modulus of pure PCL is approximately 4.5 MPa, which is significantly lower than that of PLA and other materials ( Popescu et al, 2018 ).…”

Synthesis of Benzoxazine Functionalized Amine‐Bridged Bis(phenolato) Rare Earth Complexes and Their Application in Ring‐Opening Polymerization of rac‐Lactide

“…Stereoregular PLAs are crystalline polymers with a high melting point, whereas atactic PLA is amorphous and brittle. Therefore, extensive efforts have been focused on the synthesis of stereoregular PLAs, [ 4‐5 ] and a variety of catalysts/initiators have been applied in the controlled ROP of rac ‐LA, including organocatalysts, [ 6‐8 ] main group metal, [ 9‐17 ] transition metal, [ 18‐20 ] and rare earth metal complexes. [ 21‐23 ] Among them, rare earth metal complexes have attracted intensive attention due to their high activity, high stereoselectivity, and good controllability for polymerization under mild conditions.…”