Browsing by Author "Heyns, Ingrid Marie"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemSynthesis and structure-property relationships of 3-methylene-2-pyrrolidone-based (co)polymers(Stellenbosch : Stellenbosch University, 2015-03) Heyns, Ingrid Marie; Pfukwa, Rueben; Klumperman, Bert; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.ENGLISH ABSTRACT: Recently, the incorporation of renewable resources as a substitute to fossil fuels in the synthesis of polymers/materials has attracted a vast amount of interest, particularly for the green advantages offered. This study describes the synthesis, polymerization and characterization of 3-methylene-2-pyrrolidone-based (3M2P) monomers, with 3M2P being a naturally occurring lactam moiety. Two different chemical syntheses of the monomer, 3M2P, were attempted, with the first approach involving the Wittig reaction for the formation of the exo-cyclic methylene group. The second approach involved the dehydration of 3-(hydroxymethyl)-2-pyrrolidone. Preference was given to the Wittig approach during the study conducted, as the dehydration reaction of the second approach was unsuccessful. The purification and control over by- and side-products of the Wittig approach were optimized and confirmed by various spectroscopic techniques. Statistical copolymerizations of 3M2P-based monomers revealed the formation of oligomers, while in situ 1H NMR spectroscopic experiments failed to quantify the incorporation or consumption of either monomers due to a peak overlap. Conventional radical homopolymerizations of 3M2P were successful and polymers were characterized by NMR spectroscopy and size exclusion chromatography (SEC). It was discovered that the polymer, P(3M2P), has very good thermal stability with a Tg = 285 °C and a decomposition temperature between 400-500 °C. P(3M2P) proved to be extremely water-soluble, but it did not dissolve in most organic solvents. The thermal and solubility behaviour were ascribed to the structurally rigid lactam moiety and its strong hydrogen-bonding ability. Cytotoxicity testing revealed that P(3M2P) was completely non-toxic. Finally, the polymerization versatility of 3M2P was evaluated via different living radical polymerization techniques in an attempt to create well-defined macromolecules with precision. SET-LRP and RAFT polymerizations proved to be controlled, with a Ð < 1.5, whilst NMP exhibited poor control. The RAFT polymerization was extended to an amphiphilic block copolymer with the first segment being polystyrene and the second segment, P(3M2P). During the chain-extension only oligomeric 3M2P species were incorporated.
- ItemThe use of 3-methylene-2-pyrrolidone-based (co)polymers in industrial and biomedical applications(Stellenbosch : Stellenbosch University, 2018, 2018-12) Heyns, Ingrid Marie; Klumperman, Bert; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.ENGLISH ABSTRACT: The primary aim of this study was to investigate the feasibility of incorporating 3-methylene-2-pyrrolidone-based (3M2P)-based (co)polymers for use in industrial applications, e.g. kinetic hydrate inhibitors and in biomedical applications, e.g. bioencapsulation of exosomes. For use as kinetic hydrate inhibitors, poly(3M2P)’s hydrophobicity was increased by expanding the ring-size, copolymerization with a hydrophobic co-monomer and N-alkylation of 3M2P. Low molecular weights and adequate disperties were attainable by using the dead end polymerization technique. Thermal phase transition temperatures of the more hydrophobic analogues were obtained via UV/Vis spectroscopy. The thermal sensitivity of a copolymer’s phase transition temperature in the presence of the Hofmeister series, was also evaluated. Double hydrophilic block copolymers, consisting of poly(N-methyl-3M2P)-block-poly(HPMAm-oligolactates) were synthesized with an azide-functional reversible addition fragmentation transfer (RAFT)-agent and the polymerizations were shown to be controlled, with relatively low dispersities. The thermally-triggered self-assembly of the block copolymer morphologies were investigated via transmission electron microscopy (TEM) and it was proved that a block copolymer with a hydrophilic mass fraction (f) of 13 % was most likely to form vesicular morphologies. The thermoresponsive aggregation was evaluated with variable 1H nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), TEM, UV/vis spectroscopy and confocal fluorescent microscopy (CFM). At a concentration of 1 mg/mL, the phase transition temperature was found to be 36.5 °C, displaying cloud point temperatures very close to physiological temperatures. Furthermore, the α-functionalities of the block copolymer was decorated with a targeting ligand and fluorescent dye via a copper-free “click” reaction. A combination of the conjugates and unfunctionalized block copolymers were found to be successful in the encapsulation of exosomes via a thermally-triggered self-assembly technique. The block copolymer appears to be a promising candidate for further investigation as a general bioencapsulation material.