Presentation Type

Poster

Keywords

computational, ring-opening, homopolymerization, copolymerization, lactide, caprolactone

Department

Chemistry

Major

Chemistry

Abstract

The mechanism for the ring-opening polymerization of lactide and ε-caprolactone is presented here with an aluminum-centered catalyst featuring a tridentate ligand and two alkoxide initiating ligands. In each homopolymerization, the addition of electron-withdrawing groups on the tridentate ligand lowers the activation energy of the reaction by increasing the electrophilicity of the central Aluminum. We further investigated the polymerizations by comparing the energy difference between copolymerization and homopolymerization following the initial ring opening as well as the potential for dual polymer chains from the insertion of both initiating ligand. Single chain polymerization is favored in every case, due to lower bond strength between the initial polymer and the Al center compared to strength of the bond between the Al center and the additional initiating ligand. This helps to explain the narrow polydispersity observed experimentally. Without the presence of EWG on the tridentate ligand, homopolymerization is favored for both polycaprolactone and polylactide. The addition of EWG, however, results in potential energy surfaces that favor the addition of lactide and single chain polymerization, regardless of the initial coordinated polymer.

Faculty Mentor

Benjamin P. Wilson

Funding Source or Research Program

Summer Undergraduate Research Program

Location

Waves Cafeteria

Start Date

23-3-2018 2:00 PM

End Date

23-3-2018 3:30 PM

Share

COinS
 
Mar 23rd, 2:00 PM Mar 23rd, 3:30 PM

Computational Investigation of the Ring-opening Homo- and Co-Polymerizations of Lactide and ε-Caprolactone

Waves Cafeteria

The mechanism for the ring-opening polymerization of lactide and ε-caprolactone is presented here with an aluminum-centered catalyst featuring a tridentate ligand and two alkoxide initiating ligands. In each homopolymerization, the addition of electron-withdrawing groups on the tridentate ligand lowers the activation energy of the reaction by increasing the electrophilicity of the central Aluminum. We further investigated the polymerizations by comparing the energy difference between copolymerization and homopolymerization following the initial ring opening as well as the potential for dual polymer chains from the insertion of both initiating ligand. Single chain polymerization is favored in every case, due to lower bond strength between the initial polymer and the Al center compared to strength of the bond between the Al center and the additional initiating ligand. This helps to explain the narrow polydispersity observed experimentally. Without the presence of EWG on the tridentate ligand, homopolymerization is favored for both polycaprolactone and polylactide. The addition of EWG, however, results in potential energy surfaces that favor the addition of lactide and single chain polymerization, regardless of the initial coordinated polymer.