Salen-Manganese Complexes and their Application in the Ring-Opening Polymerization of Lactide and ϵ-Caprolactone

Recent progress in nanocomposites of carbon dioxide fixation derived reproducible biomedical polymers

In recent years, the environmental problems accompanying the extensive application of biomedical polymer materials produced from fossil fuels have attracted more and more attentions. As many biomedical polymer products are disposable, their life cycle is relatively short. Most of the used or overdue biomedical polymer products need to be burned after destruction, which increases the emission of carbon dioxide (CO₂). Developing biomedical products based on CO₂ fixation derived polymers with reproducible sources, and gradually replacing their unsustainable fossil-based counterparts, will promote the recycling of CO₂ in this field and do good to control the greenhouse effect. Unfortunately, most of the existing polymer materials from renewable raw materials have some property shortages, which make them unable to meet the gradually improved quality and property requirements of biomedical products. In order to overcome these shortages, much time and effort has been dedicated to applying nanotechnology in this field. The present paper reviews recent advances in nanocomposites of CO₂ fixation derived reproducible polymers for biomedical applications, and several promising strategies for further research directions in this field are highlighted.

One-Pot Precision Synthesis of AB, ABA and ABC Block Copolymers via Switchable Catalysis

The switchable catalysis using a commercial salenMn catalyst was firstly developed and applied in the one-pot selective copolymerization from anhydrides, epoxides, CO₂ and ϵ-caprolactone (ϵ-CL) mixtures for the precise synthesis of AB, ABA and novel ABC block copolymers. The observed unique double switch process comprising three different polymerization cycles was rationalized by theoretical calculations. Surprisingly, the first block turned out to be an efficient macromolecular initiator for the consecutive introduction of carbonate linkages into copolymers, albeit with dominant cyclization with the catalyst alone. Further, through the selective reaction on different epoxides, the switchable copolymerization of up to five monomers was achieved yielding well-defined multi-block copolymers with structural diversity and functionality.

Ring-opening polymerization of rac-lactide catalyzed by magnesium and zinc complexes supported by an NNO ligand

Preparation of magnesium and zinc complexes containing unsymmetric tertiary amine ligands and their catalytic properties for polymerization of rac-lactide.

Monomer Controlled Switchable Copolymerization: A Feasible Route for the Functionalization of Poly(lactide)

Switchable polymerization is an attractive strategy to enable the sequential selectivity of multi-block polyesters. Besides, these well-defined multi-block polyesters could enable further modification for wider applications. Herein, based on the reversible insertion of CO₂ by Salen-Mn^III , a new monomer controlled self-switchable polymerization route was developed. Chemoselective ring opening copolymerization of O-carboxyanhydrides (OCAs) and lactide (LA) was explored without cocatalyst. The sequential conversion of OCAs and LA into the polymer chain could form multi-block polyesters. Based on this strategy, a series of multi-block polyesters with different pendant groups were synthesized. Furthermore, by modifying the propargyl-containing copolymers with quaternary ammonium groups, we have realized antibacterial functionalization of PLA. These results imply the potential application of this strategy for the fabrication of functional polymers for biomedical applications.