Aliphatic polyesters are a class of materials that receives much attention in academia as well as industry due to promising material properties which are comparable to some commodity plastics but come along with the advantage of (bio)degradability. Ring-opening polymerization (ROP) of cyclic esters offers simple access to these polymers and numerous metal-based catalysts have been reported to date. However, it still remains a challenge to combine high catalytic activity with control over polymerization and achieve a broad monomer scope simultaneously. In this contribution, we present an indium alkoxide complex supported by a salan-type framework that shows very high rates, excellent polymerization control, high tolerance against chain transfer agents and yields high molecular weight (bio)degradable polymers via ROP of several cyclic esters. Additionally, the use of impure lactide feedstock is also tolerated. An air-stable indium chloro pre-catalyst showed only low catalytic activities, however, it could be converted in situ into a highly active alkoxide species. Besides synthesis of homopolymers, the novel indium initiator is also capable of producing precise copolymers. Depending on the choice of lactones, one-pot monomer mixtures generate either gradient copolymers or well-defined block copolymers demonstrating the versatility of the presented indium salan complex.

Indium salan catalysts: Very high activities in the ring-opening polymerization of various cyclic esters and synthesis of well-defined copolymers from monomer mixtures

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.