A simple zinc catalyst showing high activity for both the synthesis of polylactide, a biodegradable polymer produced from renewable feedstock, and its degradation was described. In the ring‐opening polymerization of lactides, the zinc catalyst showed one of the highest activities reported in the literature for reactions carried out in solution at room temperature. This excellent performance was preserved even when the process was performed under industrial conditions: at high temperature, in the absence of solvent, and by using a low catalyst loading with unpurified monomers. The same complex revealed high efficiency also in depolymerization of polylactide by alcoholysis, a process that occurred efficiently at room temperature and in the absence of solvent, conditions that reduce costs and guarantee low environmental impact.

Two dinuclear aluminum complexes bearing dinaphthalene bridging Schiff bases have been synthesized and investigated as catalysts in ring-opening polymerization (ROP) of cyclic esters such as rac-lactide (rac-LA) and ε-caprolactone (ε-CL) and in the copolymerization (ROCOP) of phthalic anhydride (PA) with cyclohexene oxide (CHO) and limonene oxide (LO). The polymerizations of cyclic esters were living, producing polymers with narrow molar mass distributions. Kinetic studies showed that the polymerizations were first order with respect to the monomers. Cooperative effects between two metal centers, located in proximal positions, are invoked to rationalize the high activities toward both monomers, although the rigid backbone of the complexes enhances the reactivity of less encumbered caprolactone in comparison to lactide. Good activities were achieved also in the copolymerization of phthalic anhydride with cyclohexene epoxide and with the bioderived limonene oxide.

In this contribution, the catalytic behavior of a phenoxy-imine aluminum catalyst and of a bimetallic salen aluminum complex in ring-opening polymerization (ROP) of macrolactones such as ω-pentadecalactone (PDL), ω-6-hexadecenlactone (HDL) and ethylene brassylate (EB), and in the ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and phthalic anhydride (PA) is described. A significant difference in terms of activity emerged between the two catalysts in the ROP of the macrolactones, while similar behaviors were observed in the ROCOP process. The synthesis of diblock polyesters, by combination of two distinct processes, was performed in a onepot procedure. The semi-aromatic polyester block was formed first, followed by the polyethylene-like portion produced by ROP of macrolactones.

Phenoxy-imine aluminum complexes, in combination with DMAP, produce efficient catalysts for the alternating copolymerization of epoxides and anhydrides. A zwitterionic species is formed in the initiation step.

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