Innentitelbild: Kontrolle über Chaos und Ordnung: Gegensätzliche Mikrostrukturen von PCL‐co‐PGA‐co‐PLA durch einen einzigen Katalysator zugänglich (Angew. Chem. 11/2022)

Abstract

Der Eisen‐Guanidin‐Katalysator zeigt eine außergewöhnliche Copolymerisationsaktivität gegenüber Lactid, Glycolid und ϵ‐Caprolacton, wie Sonja Herres‐Pawlis, Moshe Kol et al. in ihrem Forschungsartikel berichten (e202112853). Je nach Reaktionstemperatur und Art der Monomerzugabe bildet er entweder hoch definierte Pentablock‐Copolymere oder fördert Umesterungen in so starkem Ausmaß, dass randomisierte Copolymere entstehen. Damit ist er ein seltenes Beispiel für einen Katalysator, der beide Mikrostrukturen beherrscht: geordnet und chaotisch.

Catalysts as Key Enablers for the Synthesis of Bioplastics with Sophisticated Architectures

“…It shows a high thermal stability and at the same time forms highly defined copolymer structures. [27] The iron guanidine catalyst efficiently produces block copolymers with different blocks lengths and architectures. For the first time, it has allowed the creation of terblock copolymers consisting of homopolymeric blocks of LA, CL and GL.…”

“… Polymerization of different lactones to block copolyesters by sequential addition with highly active catalysts. [ 25 , 27 ] …”

“… Polymerization of different lactones to random copolyesters by equalized reactivity ratios (Al catalyst) or by enhanced transesterifications (Fe catalyst). [ 27 , 29b ] …”

“…Furthermore, it was found that the transesterifications preferably take place at the GL repeating unit possibly due to steric reasons. [27] It is astonishing that after more than five decades of lactone copolymerization still mechanistic features are revealed. It shows the high complexity of copolymerization systems and the need for further research on mechanistic details to control copolymerization in a way the desired product is obtained.…”

“…As the ROP with iron guanidine catalysts is a living polymerization following the coordination‐insertion mechanism,[ 13b , 27 ] the growth of the PLA chain can be interrupted (and later resumed) for the formation of the active species accompanied with the iron(III) species. Since the duties of the iron(II) and iron(III) species are well separated, both polymerization mechanisms can work hand in hand without disturbing each other.…”