A Comparison of Gallium and Indium Alkoxide Complexes as Catalysts for Ring-Opening Polymerization of Lactide

Abstract

ABSTRACT:The synthesis, characterization, and reactivity of an aluminum alkoxide complex supported by a ferrocene-based ligand, (thiolfan*)Al(O t Bu) (1 red , thiolfan* = 1,1'-di(2,4-di-tert-butyl-6-thiophenoxy)ferrocene), are reported. The homopolymers of L-lactide (LA), ε-caprolactone (CL), δ-valerolactone (VL), cyclohexene oxide (CHO), trimethylene carbonate (TMC), and their copolymers were obtained in a controlled manner by using redox reagents. Detailed DFT calculations and experimental studies were performed to investigate the mechanism. Mechanistic studies show that after the insertion of the first monomer, the coordination effect of the carbonyl group, which has usually been ignored in previous reports, can significantly change the energy barrier of the propagation steps, thus playing an important role in polymerization and copolymerization processes.

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

“…Compound 326 also proved to be efficient in the ROP of ε-CL and in the CL/LA copolymerization. Similar Salen-based complexes exhibiting poor activity were concomitantly reported by Mehrkhodavandi et al [142]. With respect to bimetallic complexes, species 332-334 proved able to catalyze the ROP of r-LA at 70-100 • C, albeit with poor stereocontrol [124].…”

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

“…Although the homopolymerization of TMC proceeds quickly at ambient temperature, elevated temperatures are required to polymerize it after l -lactide due to the nature of the intermediate formed after the ring opening of lactide that features a five-membered chelate. 32 , 52 – 57 This difference in shifting the polymerization of TMC from room temperature, as in the case of PLA- b -PTMC ( Table 1 , entry 3), to elevated temperatures, as in the case of PTMC- b -PLA ( Table 1 , entry 4), manifests itself in the broadening of the molar mass distributions ( Fig. 5 ).…”

Synthesis and structures of mono- and di-nuclear aluminium and zinc complexes bearing α-diimine and related ligands, and their use in the ring opening polymerization of cyclic esters

“…Indeed, we note that in reports by other groups, the formation of M-OR species from parent a chloride complex required salt metathesis via the use of Na (or K) alkoxides, rather than by direct reaction with alcohols. [24] Concerning the effect of the metal center (zinc versus aluminium), slightly lower conversions and polymer Mn were observed in the presence of the Zn-species 6 at 30 ºC, compared to the values obtained when using the Al-derivative 1 (cf. runs 7 and 1).…”