Polyethylene-based Polar Block Copolymers Preparation using Organometallic-Mediated Radical Polymerization

The synthesis of polyethylene-polar block copolymers presents significant challenges due to the different reactivity of the monomers involved. The difference in reactivity required several polymerization techniques. The Co(salen) offers reactivities in mediating the polymerization of various monomers. This study addressed these challenges by employing polymer-Co(salen) complexes and conducting the synthesis of several polyethylene-b-polar polymers using only the radical approach. The research was divided into six chapters. Chapter 1 underscored the importance of polyethylene-polar block copolymers and introduced controlled radical polymerization techniques, including organocobalt-mediated radical polymerization. Chapter 2 explored the preparation of a polymer-Co(salen) complex with chain-end fidelity. Kinetic studies of Co(salen) mediated radical polymerization and propagation resumption reactions concluded that the polymer-Co(salen) complexes with chain-end fidelity were produced for methyl acrylate, vinyl acetate, and N, N- dimethyl acrylamides. Chapter 3 examined the reactivity of polymer-Co(salen) complexes, polar monomers, and ethylene monomers. TEMPO trapping experiments implied that the polymer-Co(salen) dormant species could initiate a radical species. Electron donors were found to coordinate with Co(salen), accelerating bond homolysis. Random copolymerization experiments suggested that radical transfer between polar monomer and ethylene was possible in the presence of Co(salen). Chapters 4, 5, and 6 reported the synthesis of PMA-b-PE, PVAc-b-PE, and PDMA-b-PE copolymers using PMA-Co(salen), PVAc-Co(salen), and PDMA-Co(salen) complexes, respectively. It was found that the degree of polymerization of ethylene increased with higher ethylene pressure, longer reaction duration, and the introduction of an electron donor, which aligned with the kinetics study. In summary, this research demonstrated the potential of preparing polyethylene-polar block copolymers using polymer-Co(salen) dormant species prepared through Co(salen) mediated radical polymerization. This method facilitated the preparation of PMA-b-PE, PVAc-b-PE, and PDMA-b-PE using one type of organometallic complexes, opening the door for an expanded scope of monomers by using Co(salen) mediated radical polymerization.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Zhao, Chenying

Advisor dc:contributor.advisor

• Harth, Eva

Committee members dc:contributor.committeemember

• Lee, Randall T
• Chen, Tai-Yen
• Comito, Robert
• Conrad, Jacinta

• Chemistry

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/19921

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/19921