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
Included in
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.