Synthesis of end-functionalized polyethylene via coordinative chain transfer polymerization and its related applications
File(s)
Author(s)
Huang, Jiakai
Type
Thesis
Abstract
This thesis establishes an integrated route to afford end-functionalised polyethylenes (f-PEs) via coordinative chain transfer polymerisation (CCTP) and demonstrates its use as reactive additives to generate bulk functionalised polymers. Using bis(imino)pyridine Fe/MAO with ZnEt2 as the chain transfer agent (CTA), Zn-terminated PE intermediate Zn(PE)2 was prepared and directly converted to polyethylene iodide (PE-I) and a family of PE ketones. PEs with sulfur functionalities were also produced but with considerable by-products due to their limited selectivity and stability.
Post-polymerisation functionalisation of PE-I afforded PE-NH2, phosphonium-functionalised PE and a polymeric diphosphine ligand PE-N(PPh2)2 that served as a soluble polymer support for chromium-based ethylene oligomerisation. PEs bearing phosphonium functionalities exhibited better thermal resistance and behaved as polymeric salts.
As functionalised additives, synthetic f-PEs were blended with commercial polymers. The films prepared from LDPE and PE ketones via solution-blending retained a strong carbonyl signature and displayed increased surface polarity with additive loading. The films prepared from LDPE and PE additives with phosphonium functionalities exhibited measurable but moderate antimicrobial performance compared to conventional systems. The materials generated by blending PET with PE-C(O)C2H4CO2Et through extrusion exhibited a viscosity decrease, which is consistent with transesterification reactions and chain scission. The films showed progressively higher surface polarity with higher additive content, which can be associated with polar chain ends generated during the process. These findings indicate that compatibilization of PET and functionalised PE additives is achieved, which also suggests that the potential applications of these additives to serve as compatibilizers for recycling or upcycling mixed PET and PE wastes.
Overall, this work links CCTP reactions, post-polymerisation functionalisation protocols and polymer blending to deliver reliable f-PEs and demonstrated their promise in providing enhanced interfacial properties, antimicrobial performance and compatibility with commercial polymers.
Post-polymerisation functionalisation of PE-I afforded PE-NH2, phosphonium-functionalised PE and a polymeric diphosphine ligand PE-N(PPh2)2 that served as a soluble polymer support for chromium-based ethylene oligomerisation. PEs bearing phosphonium functionalities exhibited better thermal resistance and behaved as polymeric salts.
As functionalised additives, synthetic f-PEs were blended with commercial polymers. The films prepared from LDPE and PE ketones via solution-blending retained a strong carbonyl signature and displayed increased surface polarity with additive loading. The films prepared from LDPE and PE additives with phosphonium functionalities exhibited measurable but moderate antimicrobial performance compared to conventional systems. The materials generated by blending PET with PE-C(O)C2H4CO2Et through extrusion exhibited a viscosity decrease, which is consistent with transesterification reactions and chain scission. The films showed progressively higher surface polarity with higher additive content, which can be associated with polar chain ends generated during the process. These findings indicate that compatibilization of PET and functionalised PE additives is achieved, which also suggests that the potential applications of these additives to serve as compatibilizers for recycling or upcycling mixed PET and PE wastes.
Overall, this work links CCTP reactions, post-polymerisation functionalisation protocols and polymer blending to deliver reliable f-PEs and demonstrated their promise in providing enhanced interfacial properties, antimicrobial performance and compatibility with commercial polymers.
Version
Open Access
Date Issued
2025-10-22
Date Awarded
2026-03-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Britovsek, George
Publisher Department
Department of Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)