Bioplastics like polylactide gain more and more significance as replacement for conventional polymers. However, not all properties can be mimicked by bio-based or biodegradable homopolymers. Therefore, copolymerization becomes an important pathway for the development of new materials. We recently presented an iron guanidine catalyst that is biocompatible, robust and shows a higher polymerization activity for lactide than the industrially used tin octoate. Taking the predicted production growth rate of polylactide into account, the replacement of the toxic tin compound by a benign catalyst becomes a necessary step. The catalyst is, furthermore, capable of copolymerizing lactide, ε-caprolactone and glycolide to defined copolymers. It becomes even more significant being additionally an active catalyst for the atom transfer radical polymerization (ATRP). Copolymerization is typically limited to a certain monomer class being polymerized via the same mechanism. Preparation of a block copolymer consisting of monomers with distinctive chemical structures typically includes different catalysts and purification steps in between to avoid deactivation of the second catalytic system leading to an uncontrolled polymerization with ambiguous copolymers. The iron guanidine complex is one of the rare catalyst examples, which can combine monomers of different classes in a copolymer by polymerizing them via different mechanisms. Block copolymers of lactide polymerized via lactone ring-opening polymerization and styrene via ATRP are obtained in a one-pot synthesis either by sequential addition or by simultaneous polymerization. Since both polymerization mechanisms proceed in a controlled manner, an adjustable polymer is synthesized. The presented catalytic system opens new pathways towards multimechanistic polymerizations and underlines that smart catalyst design improves conventional intensive polymerization procedures.

Multimechanistic polymerization: Iron guanidine complex combines ATRP with ROP

ACS Spring Meeting 2021

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