Abstract
The effect of ligand structure on the catalytic activity of amine-bis(phenolate) chromium(III) complexes in the ring-opening copolymerization of phthalic anhydride and a series epoxides was studied. Eight complexes differing in the donor-pendant group (R1) and substituents (R2) in phenolate units were examined as catalysts of the model reaction between phthalic anhydride and cyclohexane oxide in toluene. They were used individually or as a part of the binary catalytic systems with nucleophilic co-catalysts. The co-catalyst was selected from the following organic bases: PPh3, DMAP, 1-butylimidazole, or DBU. The binary catalytic systems turned out to be more active than the complexes used individually, and DMAP proved to be the best choice as a co-catalyst. When the molar ratio of [PA]:[epoxide]:[Cr]:[DMAP] = 250:250:1:1 was applied, the most active complex (R1-X = CH2NMe2, R2 = F) allowed to copolymerize phthalic anhydride with differently substituted epoxides (cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, phenyl glycidyl ether, propylene oxide, butylene oxide, and epichlorohydrin) within 240 min at 110 °C. The resulting polyesters were characterized by Mn up to 20.6 kg mol−1 and narrow dispersity, and they did not contain polyether units.
Highlights
The ring-opening copolymerization (ROCOP) of cyclic anhydrides and epoxides is a modern method of synthesis of polyesters that can provide the polymers characterized by the high molecular weight and narrow dispersity [1,2]
The goal of our research was to determine the relationship between the structure of chromium(III) amine-bis(phenolate) complexes and their catalytic activity in the ROCOP reactions of epoxides with cyclic anhydrides
Our observations are in contrast to the results described previously by the Kozak’s group [41] which found that the exchange of R2 substituents in the amine-bis(phenolate) chromium(III) complexes having [ONNO]-type ligands with R1 -X = 2-pyridyl from tBu groups for OCH3 ones resulted in approximately four-fold increase in the reaction rate
Summary
The ring-opening copolymerization (ROCOP) of cyclic anhydrides and epoxides is a modern method of synthesis of polyesters that can provide the polymers characterized by the high molecular weight and narrow dispersity [1,2]. Due to the great variety of commercially available co-monomers, the ROCOP of cyclic anhydrides and epoxides seems to be a more universal method of polyester synthesis compared to a ring-opening polymerization (ROP) of lactones. The former can deliver both aliphatic and semi-aromatic polyesters, and the latter only the aliphatic ones [1,2]. Polyesters with properties strictly dedicated to specific applications can be obtained [3]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
