The goal of this project was to develop a non-toxic amphiphilic diblock copolymer nanoparticulate drug delivery system that will solubilize paclitaxel (PTX) and retain the drug in plasma. Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (MePEG-b-PCL) diblock copolymers loaded with PTX were characterized and their physicochemical properties were correlated with their performance as nanoparticulate drug delivery systems. A series of MePEG-b-PCL was synthesized with PCL blocks ranging from 2-104 repeat units and MePEG blocks of 17, 44 or 114 repeat units. All copolymers were water soluble and formed micelles except MePEG₁₁₄-b-PCL₁₀₄, which was water insoluble and formed nanospheres. Investigation of the effects of block length on the physicochemical properties of the nanoparticles was used to select appropriate copolymers for development as PTX nanoparticles. The critical micelle concentration, pyrene partition coefficient and diameter of nanoparticles were found to be dependent on the PCL block length. Copolymers based on a MePEG molecular weight of 750 g/mol were found to have temperature dependent phase behavior. Relationships between the concentration of micellized drug and the compatibility between the drug and core-forming block, as determined by the Flory-Huggins interaction parameter, and PCL block length were developed. Increases in the compatibility between PCL and the drug, as well as longer PCL block lengths resulted in increased drug solubilization. The physicochemical properties and drug delivery performance characteristics of MePEG₁₁₄-b-PCL₁₉ micelles and MePEG₁₁₄-b-PCL₁₀₄ nanospheres were compared. Nanospheres were larger, had a more viscous core, solubilized more PTX and released it slower, compared to micelles. No difference was seen in the hemocompatibility of the nanoparticles as assessed by plasma coagulation time and erythrocyte hemolysis. Micellar PTX had an in vitro plasma distribution similar to free drug. The majority of micellar PTX associated with the lipoprotein deficient plasma fraction (LPDP). In contrast, nanospheres were capable of retaining more of the encapsulated drug with significantly less PTX partitioning into the LPDP fraction. In conclusion, although both micelles and nanospheres were capable of solubilizing PTX and were hemocompatible, PTX nanospheres may offer the advantage of prolonged blood circulation, based on the in vitro plasma distribution data, which showed that nanospheres retained PTX more effectively. / Pharmaceutical Sciences, Faculty of / Graduate

Highly crosslinked epoxy resin systems are essential in aerospace applications due to the high operating temperatures. Although highly crosslinked epoxy resins have the required glass transition temperature (Tg) for the application, they are inherently brittle and matrix toughness is improved by incorporation of a second phase. Previous studies have focused mostly on toughening of lightly crosslinked epoxy systems, whereas this study investigates toughening of a highly crosslinked epoxy resin system using thermoplastic toughners poly(ether sulfone) (PES) and a poly(methyl methacrylate)-b- poly(butyl acrylate)-b-poly(methyl methacrylate) (MAM) block copolymer (BCP).

The aim of this research is to fabricate an electrically conducting, smooth, continuous and sensitive nanofiber using tri-block copolymer PS-b-PDMS-b-PS and SWCNTs by electrospinning. The electronic nanofibers may be utilized for effective biosensing applications. The SWCNTs have been of great interest to researchers because of their exceptional electrical, mechanical, and thermal properties. The nanoscale diameter, high aspect ratio, and low density make them an ideal reinforcing candidate for novel nanocomposite material. Electrically conducting fibers are prepared by electrospinning a solution of PS, PS-b- PDMS-b-PS and functionalized SWCNTs using solvent DMF. The fibers formed have an average diameter and height of 5 and 4 μm respectively. These fibers are characterized by SEM, AFM, and optical microscopy. The electrical characterization of a single fiber shows an almost linear graph of current vs. voltage using the Kelvin Sensing method. This linear graph exemplifies the conducting nature of the fiber. Future work includes preparing nanofibers decorated with functional groups and binding with specific type of enzyme or protein to study their I-V behavior. This approach or method can be utilized for bio-sensing activities, especially for the detection of various antibodies and protein molecules.

Nature is an excellent design that inspires scientists to develop smart systems. In the realm of separation technology, biological membranes have been an ideal model for synthetic membranes due to their ultrahigh permeability, sharp selectivity, and stimuliresponse. In this research, fabrications of bioinspired membranes from block copolymers were studied. Membranes with isoporous morphology were mainly prepared using selfassembly and non-solvent induced phase separation (SNIPS). An effective method that can dramatically shorten the path for designing new isoporous membranes from block copolymers via SNIPS was first proposed by predetermining a trend line computed from the solvent properties, interactions and copolymer block sizes of previously-obtained successful systems. Application of the method to new copolymer systems and fundamental studies on the block copolymer self-assembly were performed. Furthermore, the manufacture of bioinspired membranes was explored using (1) poly(styrene-b-4-hydroxystyrene-b-styrene) (PS-b-PHS-b-PS), (2) poly(styrene-bbutadiene- b-styrene) (PS-b-PB-b-PS) and (3) poly(styrene-b-γ-benzyl-L-glutamate) (PSb- PBLG) copolymers via SNIPS. The structure formation was investigated using smallangle X-ray scattering (SAXS) and time-resolved grazing-Incidence SAXS. The PS-b- PHS-b-PS membranes showed preferential transport for proteins, presumably due to the hydrogen bond interactions within the channels, electrostatic attraction, and suitable pore dimension. Well-defined nanochannels with pore sizes of around 4 nm based on PS-b- PB-b-PS copolymers could serve as an excellent platform to fabricate bioinspired channels due to the modifiable butadiene blocks. Photolytic addition of thioglycolic acid was demonstrated without sacrificing the self-assembled morphology, which led to a five-fold increase in water permeance compared to that of the unmodified. Membranes with a unique feather-like structure and a lamellar morphology for dialysis and nanofiltration applications were obtained from PS-b-PBLG copolymers, which exhibited a hierarchical self-assembled morphology with confined α-helical polypeptide domains. Our results suggest that bioinspired nanochannels can be designed via block copolymer self-assembly using classical methods of membrane preparation. Investigation of the membrane formation mechanism leads us to a better understanding of the design strategies for the development of self-assembled nanochannels from block copolymers. In further outlook, our research could give a contribution to the discovery of future generation materials for water purification and desalination, as well as biological separation.

The primary aim of this work is to explore the potential applications of isoporous block copolymer membranes. Block copolymers (BCPs) have demonstrated their versatility in the formation of isoporous membranes. However, application spectrum of these isoporous membranes can be further broadened by exploring the technical aspects, such as desired surface chemistry, well-defined pore size, appropriate pore density, stimuli responsive behavior, and by imparting desired functionalities through chemical modifications. We believe, by exploring these possibilities, isoporous membranes hold tremendous potential as high performance next generation separation membranes. Motivated by these attractive prospects we systematically investigated novel routes for modification of isoporous membranes and their implications on properties and performance of the membranes for various applications. In this work, polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) has been selected to fabricate isoporous membranes using non-solvent induced phase separation (NIPS). We selected PS-b-P4VP since its well-defined isoporous morphology is studied in detail and it is extensively characterized. In order to further widen the application bandwidth of BCP membranes, it is desirable to integrate different functionalities in the BCP architecture through a straightforward approach like post-membrane-modification or fabrication of composite membranes to impart anticipated functionalities. The most critical challenge in this approach is to retain the well-defined nanoporous morphology of BCP membranes. We focused on exploring new routes for chemical functionalization of isoporous PS-b-P4VP membranes via various in-situ and post-membrane fabrication approaches. To date, most of the work reported in the literature on PS-b-P4VP presented different routes to fabricate isoporous membranes and their conventional performance in liquid separations. Few efforts have been dedicated to alter the chemistry of PS-b-P4VP membranes by tuning the reactivity of the chemically active P4VP block or the surface chemistry to enhance the membrane performance for desired applications. During the Ph.D. study, we primarily focused on: (i) post modification approach, (ii) surface modification and (iii) in-situ membrane modification approach for fabrication of the mixed-matrix nanoporous membranes without altering the isoporous morphology of the membrane. The membranes fabricated using the mentioned above routes were tested for different applications like stimuli-responsive separations, self-cleaning membranes, protein separations and high-performance humidity sensors.

Thesis is focused on structural study of ethylene-propylene copolymers (E/P copolymers) produced by gas phase polymerization. Goal of work was to determine the effect of used catalysts on the distribution of ethylene units in the resulting material. Three E/P copolymers were prepared on commercial Ziegler Natta catalysts with diether or phthalate based internal donors. The copolymers were fractionated according crystallization ability and molar mass. Next, the mass content and the distribution of the ethylene units in the copolymer were determined in each fraction by nuclear magnetic resonance (NMR). Together with other structural analytical methods, phthalate internal donor has been found to produce ethylene blocks under certain conditions, while the diether ID lacks this ability.

This diploma thesis deals with the isolation and characterization of copolymer P(3HB-co-4HB). The teoretical part was prepared as a literature search which describe polyhydroxyalkanoates in general, their structure, synthesis, degradation and isolation. Furthermore, copolymers containing 4HB units are mentioned in this thesis and there is also no mentioned of the biosynthesis and biodegradation of copolymer P(3HB-co-4HB). The first aim of this diploma thesis was to find out which solvent is the best for copolymer extraction and then characterize obtained copolymer P(3HB-co-4HB). The isolated copolymer was characterized by gas chromatography, SEC-MALS, thermal analysis and SEM. In the second part of the thesis, release of model biologically active substance from the PHA films was studied. Rhodamine 6G dye was selected for the simulation, which was used to stain the copolymer films and the P(3HB) films. It was observed that film prepared from P(3HB-co-4HB) copolymer released entrapped substance much faster than film made from P3HB homopolymer, and, in addition, the copolymer was substantially more susceptible to enzyme degradation.

Isoporous membranes are attractive for the regulation and detection of transport at the molecular level. A well-defined asymmetric membranes from diblock copolymers with an ordered nanoporous membrane morphologies were fabricated by the combination of block copolymer self-assembly and non-solvent-induced phase separation (NIPS) technique. This is a straightforward and fast one step procedure to develop integrally anisotropic (“asymmetric”) membranes having isoporous top selective layer. Membranes prepared via this method exhibit an anisotropic cross section with a thin separation layer supported from underneath a macroporous support. These membrane poses cylindrical pore structure with ordered nanopores across the entire membrane surfaces with pore size in the range from 20 to 40 nm. Tuning the pore morphology of the block copolymer membranes before and after fabrication are of great interest. In this thesis, we first investigated the pore morphology tuning of asymmetric block copolymer membrane by complexing with small organic molecules. We found that the occurrence of hydrogen-bond formation between PS-b-P4VP block copolymer and –OH/ –COOH functionalized organic molecules significantly tunes the pore morphology of asymmetric nanoporous membranes. In addition, we studied the complexation behavior of ionic liquids with PS-b-P4VP block copolymer in solutions and investigated their effect on final membrane morphology during the non-solvent induced phase separation process. We found that non-protic ionic liquids facilitate the formation of hexagonal nanoporous block copolymer structure, while protic ionic liquids led to a lamella-structured membrane. Secondly, we demonstrated the catalytic activity of the gold nanoparticle-enhanced hollow fiber membranes by the reduction of nitrophenol. Also, we systematically investigated the pore morphology of isoporous PS-b-P4VP using 3D imaging technique. Thirdly, we developed well-distributed silver nanoparticles on the surface and pore walls of PS-b-P4VP block copolymer membranes and then investigated the biocidal activity of the silver nanoparticles grown membranes. Finally, a novel photoresponsive nanostructured triblock copolymer membranes were developed by phase inversion technique. In addition, the photoresponsive behavior on irradiation with light and their membrane flux and retention properties were studied.

This diploma thesis is focused on study of polymerization of hexa-1,5-diene catalyzed by phenoxy-imine titanium dichloride (FI Ti) and methylaluminoxane (MAO) as cocatalyst. Effect of monomer concentration, polymerization temperature and cocatalyst/catalyst ratio on catalytic activity, molecular weights, polydispersities and particularly microstructure of prepared poly(hexa-1,5-diene) was studied. 1H NMR spectroscopy revealed that the poly(hexa-1,5-diene) microstructure contained methylene-1,3-cyclopentane (MCP) as well as vinyl tetramethylene (VTM) units. Kinetics of this polymerization was studied. Finally, copolymer of ethene and hexa-1,5-diene possessing incorporated pendant vinyl group was prepared.

Fluorinated polymers are niche macromolecules that play an essential role in modern life. The special properties of fluorine, including among others, a large electronegativity (ca 3.98), low polarisability, small van der Waal’s radius (135 pm) and the strong C-F bond (ca 485 kJ · mol−1), impart unique properties to organofluorine compounds. Flu-oropolymers exhibit a combination of desirable traits, including high thermal stability, low coefficient of friction, chemical inertness, oleo- and hydrophobicity, and low surface tension. Among the fluoropolymers, polyvinylidene fluoride (PVDF), and copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), have found applications in the coatings industry as the binder in exterior coatings. The chemical inertness of poly(VDF-co-HFP) copolymer, however, prevents disper-sion of pigments into the coating and also inhibits adhesion of the coating onto substrates. An acrylic modifier polymer is typically added to the poly(VDF-co-HFP) copolymer to improve the dispersion of pigments and the adhesion of the coating. This acrylic copoly-mer is physically blended with the poly(VDF-co-HFP) copolymer on a macromolecular scale (i.e. it forms a thermodynamically miscible blend). The loading of acrylic copolymer in commercial PVDF coatings is often in the range of 20 to 30 % by weight of polymer solids. Typically, copolymers of methyl methacrylate, ethyl acrylate and methacrylic esters are employed. Alternative strategies to overcome the adhesion problem include, among others, chem-ical modification of the surface of the fluoropolymer film. This can be achieved by graft copolymerisation or core shell emulsion polymerisation. These methods are used to funcionalise the polymer chains, while maintaining the desirable properties of the parent polymer. Due to environmental regulations, industry focus has shifted towards develop-ing coatings with a low volatile organic compound (VOC) content. Aqueous, low VOC, air-drying coatings can be formulated directly from the acrylic modified fluoropolymer (AMF) latex and have superior properties to solvent based, high VOC, air-dry coatings. Their advantages include low viscosities, reduced flammability, reduced odour and easy application using conventional equipment. A large portion of the aqueous coatings are sold into the architectural market with over 70 % of architectural paints used in the United States being classified as aqueous. Arkema Inc. has developed a commercial aqueous fluoropolymer latex using the method of seeded emulsion polymerisation. VDF and HFP monomers are randomly copolymerised via emulsion polymerisation. This poly(VDF-co-HFP) copolymer may be used as the seed material in a core-shell polymerisation using acrylic monomers. Kato et al. [49] discloses the preparation of an AMF formulation for poly(VDF-co-HFP) copoly-mer. Preliminary testing of membrane textiles coated with such formulations showed that the AMF coatings degrade under UV irradiation more rapidly than is is expected for poly(VDF-co-HFP) copolymer. The patent indicates that the nature of the product formed by the emulsion polymerisation is not well understood and the product my be either a graft copolymer of a core-shell system. The aim of this research reported in this dissertation was to shed light on the nature of the final product, and to verify the claims made in the above-mentioned patent. Various acrylic monomers were copolymerised via seeded emulsion polymerisation us-ing commercial poly(VDF-co-HFP) copolymer as the seed material. The concentration and the ratios of the monomers were varied according to the formulation guidelines in Kato et al.[49]. ATR-FTIR spectroscopy and19F NMR spectroscopy was used to de-termine the microstructure of the resultant latexes. ATR-FTIR spectra confirmed the presence of C=C and C=O bonds in latexes. This indicates that unreacted acrylic com-ponents are present. The ATR-FTIR spectra of the films indicated the disappearance of the C=C bonds from the latex, which indicates that the monomers are evaporated easily from the latexes during film formation. The 19F NMR spectra confirmed that no modi-fication of the poly(VDF-co-HFP) copolymer backbone took place during the reactions. The particle size distribution graphs showed an increase particle sizes and this suggested that some self polymerisation of the monomer occurred. The viscosity of the latexes were lower compared to the due to the experiments being conducted under dilution. The flow characteristics of the poly(VDF-co-HFP) copolymer was also influenced with some reactions yielding shear thickening latexes as compared to the shear thinning poly(VDF-co-HFP) copolymerc. The reactions also yielded latexes which displayed lower and higher surface tensions than the poly(VDF-co-HFP) copolymer. Therefore, the conclusion may be drawn from this work that core-shell formation occurred during the emulsion copolymerisation, as opposed to grafting of the monomer onto the poly(VDF-co-HFP) copolymer backbone. The claims made in the literature could not be substantiated; in particluar, the reported improvements in film forming ability were not realised. No commercially useful advantage exists for the emulsion copolymerisation of poly(VDF-co-HFP) copolymer with acrylic monomers over the solution blending of poly(VDF-co-HFP) copolymer with acrylic copolymers. / Dissertation (MEng)--University of Pretoria, 2019. / Chemical Engineering / MEng / Unrestricted