Improvement in aluminum complexes bearing a Schiff base in ring-opening polymerization of ε-caprolactone: the synergy of the N,S-Schiff base in a five-membered ring aluminum system

Abstract

A series of five-membered ring aluminum complexes bearing thiol-Schiff base ligands were synthesized, and their application in the ring-opening polymerization of ε-caprolactone (CL) was investigated.

Ring-Opening Polymerization of ε-Caprolactone Utilizing Aluminum Alkyl Complexes Bearing Dianionic Scorpionate Ligands

“…81,82 c Molecular weights determined by 1 H NMR spectroscopy following established procedures. 81 molecular weights seen for 7a and 8a. With respect to PDIs, values between 1.63 and 2.35 were observed.…”

“… a Conditions: Toluene, 1 M ε-CL, 1 h. All entries are the average of multiple runs with a standard deviation ≤ 2.5%. b Conversions determined by 1 H NMR spectroscopy following established procedures. , c Molecular weights determined by 1 H NMR spectroscopy following established procedures. For the high molecular weight PCL polymers generated in the absence of co-catalyst, reliable integrations for the ethyl end groups could not be obtained due to their relatively small size in comparison to the monomer subunits. , d Molecular weights determined by GPC/SEC. e The alcohol was added to the aluminum species and stirred for 5 min prior to addition of ε-CL in order to pre-activate the catalyst. …”

“… c Molecular weights determined by 1 H NMR spectroscopy following established procedures. For the high molecular weight PCL polymers generated in the absence of co-catalyst, reliable integrations for the ethyl end groups could not be obtained due to their relatively small size in comparison to the monomer subunits. , …”

“… a Conditions: Toluene, [Al]:[ i PrOH]:[ε-CL] = 1:1:100 or 1:0:100, 1 M ε-CL, 1 h. All entries are the average of multiple runs with a standard deviation ≤ 2.5% b Conversions determined by 1 H NMR spectroscopy following established procedures. For the high molecular weight PCL polymers generated in the absence of co-catalyst, reliable integrations for the ethyl end groups could not be obtained due to their relatively small size in comparison to the monomer subunits. , c Molecular weights determined by 1 H NMR spectroscopy following established procedures. , d Molecular weights determined by GPC/SEC. …”

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

“…Aluminum complexes of bidentate thiol Schiff bases have shown interesting activity as catalysts in the ROP of ε-CL ( Figure 39, Table 9) [117]. In particular, when complex 239 was activated by two equiv./Al of BnOH, almost complete conversion of 100 equiv.…”