High-Throughput Approach in the Ring-Opening Polymerization of β-Butyrolactone Enables Rapid Evaluation of Yttrium Salan Catalysts

Abstract

Poly(3-hydroxybutyrate) (PHB) is a material produced naturally by bacteria but is also chemically accessible via ring-opening polymerization (ROP) of β-butyrolactone (β-BL). In ROP, catalyst design plays a key role in the production of PHB with different stereomicrostructures, i.e., syndiotactic, isotactic, or atactic PHB. In this work, we demonstrate a simple procedure for generating the catalysts in situ by conveniently combining a suitable yttrium precursor with the respective salan pro-ligand. This approach circumvents the elaborate isolation of the catalyst and enables the high-throughput screening of a library of yttrium salan catalysts for the ROP of β-BL. Electronic and steric influences of the ligand framework on stereoselectivity and activity of the catalyst as well as limitations could be determined, and structure–property relationships were established. Depending on the substitution pattern, these in situ-generated catalysts produced syndiotactic-enriched, isotactic-enriched, or atactic PHB with high activity.

Ring‐opening (co)polymerization strategies of selected oxacyclic monomers to control and provide tailored polymers with desired properties

“…The in situ-generated catalysts produced syndiotactic-enriched, isotactic-enriched, or atactic PBL. 80 In the same year, the enantioselective chemistry of β-BL polymerization using catalysts among other enzymes was reviewed by Tong et al 81 It was mentioned, that enzyme-mediated enantioselective ROP of β-BL could only produce low molar mass polymers. β-BL was also polymerize with the use of N-heterocyclic carbene-carbodiimide (NHC-CDI) betaines as organocatalysts.…”

Copolymerization of β‐Butyrolactones into Functionalized Polyhydroxyalkanoates Using Aluminum Catalysts: Influence of the Initiator in the Ring‐Opening Polymerization Mechanism

“…[ 17–20 ] These polymerizations have been mainly mediated by anionic initiators, or by discrete metal complexes, the latter ones affording a better control of the polymer features, especially in terms of dispersity and stereoregularity of the polymers microstructure. In particular, organometallic compounds of different metals such as yttrium, [ 21–25 ] lanthanum, [ 26 ] titanium, zirconium and hafnium, [ 27,28 ] chromium, [ 29,30 ] tin, [ 31–36 ] magnesium, [ 37 ] aluminium, [ 38–43 ] zinc, [ 37,44 ] and indium, [ 45 ] have been described as active catalysts for the ROP of BBL.…”