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Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques
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_ | 1867613936588685312 |
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| access_status_str | Open Access |
| author | Carstens, Althea |
| author2 | Lederer, Albena |
| author_browse | Carstens, Althea Lederer, Albena |
| author_facet | Lederer, Albena Carstens, Althea |
| author_sort | Carstens, Althea |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134568 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:04.029Z |
| 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:10019.1/134568 Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques Carstens, Althea Lederer, Albena Pfuwka, Helen Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Biopolymers -- Synthesis Molecular structure Mass spectrometry Analytical chemistry Thesis (PhD)--Stellenbosch University, 2025. Carstens, A. 2025. Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/81010fa0-4025-4305-8cd3-f9a8070cfd57 ENGLISH ABSTRACT: This study describes the synthesis, characterisation, and self-assembly of bio-derivable copolymers incorporating guaiacyl itaconate (IAnG), a novel lignin-derived monomer. IAnG was prepared via a solventless ring-opening reaction between itaconic anhydride and guaiacol, producing α- and β-regio-isomers whose ratios could be controlled by reaction temperature. Homopolymerisation proved inefficient as only low-molecular-weight products were obtained, reflecting the inherently slow propagation of sterically demanding itaconate monomers. To address these limitations, IAnG was incorporated into copolymer systems. A series of five poly(guaiacyl itaconate-co-methyl methacrylate) [p(IAnG–MMA)] copolymers were prepared by conventional radical polymerisation with varying IAnG content, yielding heterogeneous copolymers with a broad chemical composition distribution. IAnG incorporation was consistently lower than in the feed and decreased even further at higher IAnG ratios, resulting in reduced conversions and molecular weights. Thermal analysis revealed that increasing IAnG content lowered the glass transition temperature (Tg) and led to earlier onset of degradation; however, the influence of molecular weight made it difficult to separate these effects from incorporation alone. In aqueous environments, the p(IAnG-MMA) copolymers exhibited distinct self-assembly behaviour. Dynamic light scattering measurements revealed the same three size populations in all p(IAnG–MMA) copolymers, independent of composition and molecular weight. This size invariance is thought to arise from charge density and electrostatic interactions associated with the IAnG units. Furthermore, transmission electron microscopy (TEM) revealed a mixture of spherical and bowl-shaped structures, with both the frequency of nano-bowl formation and the size of the openings increasing systematically with IAnG incorporation. Multi-detector asymmetric flow field flow fractionation (AF4) supported these findings, showing predominantly spherical assemblies at low IAnG incorporation, while copolymers with higher IAnG content exhibited a gradual evolution in morphology along the elution profile, indicating the coexistence of multiple structures within the same sample. Lastly, a fully bio-derivable copolymer system was developed by replacing methyl methacrylate with stearyl acrylate (SA), a renewable monomer from stearic acid. Six poly(guaiacyl itaconate–co–stearyl acrylate) [p(IAnG-SA] copolymers were synthesised via conventional radical polymerisation. At low IAnG feeds, incorporation was near-ideal, producing random copolymers with compositions closely matching the feed. However, at higher IAnG content (> 50 mol%), the conversion and molecular weight decrease, and a secondary SA-rich, low-molecular-weight oligomer emerged. Differential scanning calorimetry revealed progressive disruption of stearyl side-chain crystallinity, with reduced melting enthalpies as IAnG content increased. However, both the crystallisation temperature (Tc ) and melting temperature (Tm) of the copolymers remained comparable to those of a stearyl acrylate homopolymer, provided the number-average molar mass (Mn) exceeded 10 kDa. Under the same aqueous self-assembly conditions, the particle size was more strongly influenced by chemical composition in the p(IAnG–SA) system than in the MMA-based system. DLS revealed a steady decrease in hydrodynamic size with increasing IAnG, a trend also evident in TEM. Across the series, exclusively nano-bowl morphologies were observed, with bowl openings enlarging systematically as IAnG incorporation increased, giving rise to increasingly anisotropic morphologies. In summary, IAnG can be integrated into both partly and wholly bio-derived copolymer systems. Despite kinetic constraints at high feed ratios, its incorporation directed the formation of unusual, tunable morphologies, highlighting the potential of lignin-derived copolymers as sustainable building blocks for functional nanomaterials. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-12-12T13:00:06Z 2025-12-12T13:00:06Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134568 en Stellenbosch University xxi, 161 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Biopolymers -- Synthesis Molecular structure Mass spectrometry Analytical chemistry Carstens, Althea Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title | Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title_full | Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title_fullStr | Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title_full_unstemmed | Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title_short | Investigation of the molecular structure and self-assembly behaviour of bio-derived polymers using advanced analytical techniques |
| title_sort | investigation of the molecular structure and self assembly behaviour of bio derived polymers using advanced analytical techniques |
| topic | Biopolymers -- Synthesis Molecular structure Mass spectrometry Analytical chemistry |
| url | https://scholar.sun.ac.za/handle/10019.1/134568 |
| work_keys_str_mv | AT carstensalthea investigationofthemolecularstructureandselfassemblybehaviourofbioderivedpolymersusingadvancedanalyticaltechniques |