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Multidimensional analysis and characterization of chain walking polyethylene
Thesis (PhD)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613836633178112 |
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| access_status_str | Open Access |
| author | Sigwinta, Mawande |
| author2 | Lederer, Albena |
| author_browse | Lederer, Albena Sigwinta, Mawande |
| author_facet | Lederer, Albena Sigwinta, Mawande |
| author_sort | Sigwinta, Mawande |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132436 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:42:28.529Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132436 Multidimensional analysis and characterization of chain walking polyethylene Sigwinta, Mawande Lederer, Albena Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Polyethylene -- Analysis Polymers -- Solubility Molecular structure Addition polymerization Thesis (PhD)--Stellenbosch University, 2025. Sigwinta, M. 2025. Multidimensional analysis and characterization of chain walking polyethylene. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/3e20c2c8-4d35-4bc2-9722-9e1f605b8362 ENGLISH ABSTRACT: In contrast to PE produced by the classical early transition metal catalysts, the PE produced by latetransition metal catalyst ranges from moderately branched semicrystalline to highly branched branch-on-branch completely amorphous PE. The extraordinarily complex molecular structure of CWPE is attributed to the monomer insertion mechanism of the catalyst. In addition to the ease of control of molecular structure, another advantage of Pd-and Ni-catalyst over the early transition metals is their low oxophilicity. However, Pd-catalysts exhibit higher tolerance to polar functional groups and faster monomer insertion rate compared to their Ni-catalyst counterpart. Herein, advanced column-based analytical techniques including interaction chromatography (IC) and size exclusion chromatography (SEC), coupled with information-rich detectors, such as differential refractometer (dRI), viscometer (Visc), multiangle light scattering detector (MALS) were employed to study the molecular structure of, firstly CWPE homopolymers. When a mobile composition of ndecane and 1,2,4-trichlorobenzene(TCB) were used, the separation of CWPE on a hypercarb was confirmed to be based on the molecular structure conformation. This information was correlated with scaling conformation results obtained using SEC. Furthermore, the influence of mobile phase composition and column temperature on the separation behaviour was demonstrated using four mobile phase compositions that are commonly used for HT-LC of polyolefins. Good sensitivity to compositional heterogeneity of the EMA copolymer were achieved in 1-decanol/oDCB, 1-decanol/TCB and n-decane /TCB. The 1-decanol/oDCB solvent gradient provided a baseline separation at 140 °C and resolved two component peaks thus indicating its higher sensitivity to intramolecular heterogeneity. Furthermore, when a normal phase silica gel column was used at ambient temperatures with n-hexane, chloroform and a chloroform that has 5% ethanol, a separation of a range of EMA copolymers with MA contents between 0.28% MA to 17.7mol% MA were separated according to their MA contents. The separation mechanism of the silica gel column was further confirmed by FTIR using a developed calibration curve. When a binary solvent composition of 1-decanol and oDCB was used in temperature gradient mode,better resolution than SGIC was achieved. Consequently, when ethylene and polar monomers are copolymerized using Pdcatalyst the resulting random copolymer exhibit functional group distributions (FGD) in addition to the BD, branch length distribution (BLD) and molar mass distribution (MMD). Herein, CWPE homopolymers were characterized by using Therefore, precise determination of these properties is essential as they dictate the end-use structure property relations, and hence, the product performance. As such, in addition to MMD, other important polymer distribution parameters are attainable when SEC is coupled with information-rich detectors, such as differential refractometer (dRI), viscometer (Visc), multiangle light scattering detector (MALS). Furthermore, IC delivers important information about the chemical composition distribution (CCD) including BD, BLD, and FGD of complex polymers. Herein, advanced SEC with multiple detection is employed in combination with LAC in solvent gradient (SGIC) and temperature gradient mode (TGIC) to investigate the influence of synthesis conditions on the molecular structure of branched PE copolymers. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-06-06T12:50:45Z 2025-06-06T12:50:45Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132436 en Stellenbosch University xvii, 115 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Polyethylene -- Analysis Polymers -- Solubility Molecular structure Addition polymerization Sigwinta, Mawande Multidimensional analysis and characterization of chain walking polyethylene |
| title | Multidimensional analysis and characterization of chain walking polyethylene |
| title_full | Multidimensional analysis and characterization of chain walking polyethylene |
| title_fullStr | Multidimensional analysis and characterization of chain walking polyethylene |
| title_full_unstemmed | Multidimensional analysis and characterization of chain walking polyethylene |
| title_short | Multidimensional analysis and characterization of chain walking polyethylene |
| title_sort | multidimensional analysis and characterization of chain walking polyethylene |
| topic | Polyethylene -- Analysis Polymers -- Solubility Molecular structure Addition polymerization |
| url | https://scholar.sun.ac.za/handle/10019.1/132436 |
| work_keys_str_mv | AT sigwintamawande multidimensionalanalysisandcharacterizationofchainwalkingpolyethylene |