<p dir="ltr">Both natural and synthetic macromolecules have gained significant attention over the last two decades as more and more applications have been developed for these types of compounds. In particular, drug delivery and sensing have seen great improvements with the use of biomimetic- and biomacromolecules. A key function for these macromolecules is selective recognition, which has evolved in nature over millions of years, but is difficult to replicate in the laboratory. An essential component of selective recognition is sequence definition of the host, which is a key characteristic found in biomolecules and is essential for the function of proteins and nucleic acids. In this work, I present new methods for creating biomimetic sequence-defined macromolecules through the synthesis of a new sequence-definable macrocycle, an amino acid-functionalized Fréchet-type sequence-defined dendrimer, and a range of new molecular cages. The molecular cages I present in this work are of varying sizes and with different endo- and exohedral functionalities intended for future use as selective recognizers.</p><p dir="ltr">The macrocycle presented in this work is the largest sequence-definable macrocycle reported to date with 20 functionalizable positions, synthesized via iterative exponential growth using a series of copper-catalyzed azide-alkyne cycloadditions (CuAACs). Synthesis of an amino acid functionalized fully sequence-defined Fréchet-type dendrimer was also attempted through a convergent synthesis via a series of CuAACs. However, in this project, I could only reach a second-generation dendron due to solubility issues. This issue should be resolvable in the future by adding solubilizing chains to the dendrons. Finally, a series of new large molecular tetrahedrons were synthesized, enabled by the development of a more facile synthesis of a previously developed vertex. This new methodology made it possible to quickly access large quantities of this key tetrahedron vertex. With the vertex, I was able to synthesize nine new molecular tetrahedrons of various sizes with pore openings of up to 33 Å and with volumes up to 17 nm³.</p>

Organic open-shell materials, which are responsive to external stimuli; such as light, electronic field, magnetic field, etc., are subject to intensive studies in recent years for their potential application in the field of organic solar cells, semiconductors, supercapacitors, singletission, non-linear optical (NLO), spintronics, and magnetic materials. As the materials with an open-shell diradical (two unpaired electrons) or polyradical (multiple unpaired electrons) character have a significant promise for next-generation optoelectronics, magnetic, and spintronic devices, it is of paramount importance to design suitable materials with tunable electronic properties. Also, a proper understanding of the molecular topology with electro-magnetic properties and correlate with quantum functionalities can move forward the field of organic photovoltaics and optoelectronics. Here, we show that controlling the radical character based on the different molecular scaffolds can lead to materials from closed-shell (all electrons are paired) low-spin (singlet state) to intermediate open-shell (multi)radical state to high-spin (triplet state) ground-state in the pristine form. In this regard, several organic donoreptor (D-A) polymeric and small molecular systems are designed and characterized. We find that the diradical character is ubiquitous in the narrow bandgap organic materials. Based on this design rule, we have reported open-shell dyes for dye-sensitized solar cells (DSCs), which show significantly red-shifted absorption in the NIR than the closed-shell counterpart dyes. Our work on the alternating D-A polymers indicate stabilization of the high-spin triplet ground-state in the neutral form, not reported for D-A type polymers. A significant delocalization of the unpaired electrons provides thermodynamic stability of the polymer, which when used in supercapacitors, a best-in-class energy density, and a long cycle life are observed. Also, we find that the spin topology can be modulated by careful selection of molecular scaffold in the extended pi-conjugated D-A polymers. Furthermore, our study on D-A macrocycles indicates that the antiferromagnetic (AFM) couplings between the unpaired electrons can be tuned by thiophene pi-spacer, developing a record polyradical character in the macromolecular systems.

The purpose of this study was to investigate the qualitative and quantitative characteristics of high molecular weight exocellular materials (biopolymer) produced in biological waste treatment systems and examine the relationship between biopolymer and sludge settling and dewatering properties. The biopolymer that interfered with sludge filtration was a high molecular weight (>10⁵) anionic biocolloid composed partially of proteins, carbohydrates and humic acids. The relationship between supernatant biopolymer and sludge settling and dewatering characteristics is system specific. Sludge dewatering rates and supernatant biopolymer concentration vary drastically as sludge pH was increased from pH 3.0 to pH 10.0. Supernatant biopolymer and sludge specific resistance increased as sludge pH increased. Particle size analysis of biological sludge showed an increase in particles with mean size less than 10 microns as sludge pH was increased. No significant relationship was observed between sludge settling and biopolymer concentration in the sludge supernatant. / Master of Science

Over the last twenty years, substantial emphasis has been placed on the development of a new class of inorganic glasses using the sol-gel approach. This technique utilizes metal alkoxide precursors such as tetraethylorthosilcate (TEOS) to build an inorganic glass matrix out of solution by a two step poly(hydrolysis-condensation) reaction mechanism. The benefits of making ceramics by this method include considerable energy savings due to the lower sintering temperatures required to form the densified glass and the ability to produce multi-component amorphous materials that can not be made through the traditional firing processes. As a result of this last possibility, polymer researchers have sought to develop spin-off hybrid inorganic-organic network systems that can be prepared by the sol-gel method using reactively functionalized oligomers and/or monomers along with the metal alkoxide precursors. These types of organically modified multi-component glasses could have enormous potential from an applications standpoint because the system's mechanical and physical features can be tailored in accordance to the organic and polymeric materials chosen. One such inorganic-organic system prepared by this procedure is the new PEK/TEOS glasses. The PEK represents the bisphenol-A polyarylene ether either ketone thermoplastic polymer endcapped with triethoxysilane functional groups. By mixing the PEK and TEOS components at different weight compositions in the starting sol-gel reaction solution, change in the mechanical properties is observed as the TEOS content is increased for the final, thin film glasses. Also, a poor extent of reaction or degree of incorporation of the PEK oligomer is revealed which has been attributed to the vitrification of the glass before the PEK endgroups have a chance to react. To alleviate this problem, thermal treatments are employed to further the sol-gel reaction and to complete the network formation in the PEK/TEOS glasses. After the thermal treatments, the change in the mechanical and physical properties are monitored, and the data reflects systematic trends in regards to the TEOS content and the temperature of the thermal treatment utilized. In addition to these results, some speculative information is provided on the temperature sensitivity and the rate of curing of the PEK/TEOS glasses during the thermal treatments. / Master of Science

The synthesis, characterization and reactivity of linear and network macromolecules by chemical modification of amorphous poly(arylene ethers) with pendant amines were investigated. A new monomer, 3-aminophenyl-bis(4-fluoro phenyl)phosphine oxide was prepared by nitration and reduction of bis(4-fluoro phenyl)phenylphosphine oxide. Statistical incorporation of pendant aryl amines into linear polymers was achieved by copolymerization of the 3-aminophenyl-bis(4-fluorophenyl)phosphine oxide with another activated dihalide monomer such as 4,4'-dichlorodiphenylsulfone and bisphenol-A. Step polymerizations employing nucleophilic aromatic substitution with a dipolar aprotic solvent, toluene as the azeotroping agent, and a slight excess of potassium carbonate as the weak base was the preferred methodology. The concentration of amines along the polymer backbone was successfully controlled by varying the ratio of 3-aminophenyl-bis(4-fluorophenyl)phosphine oxide monomer relative to the other comonomers. Characterization of the pendant amines by proton NMR and potentiometric titration indicated good agreement between the charged amount and the incorporation of this monomer into the copolymer backbone. The pendant amines could be quantitatively converted to pendant phthalimides by reaction with phthalic anhydride. The pendant amines were also reacted to form crosslinkable groups such as maleimides and phenylethynyl phenyl imides. These were thermally treated to induce crosslinking and formed ductile networks which had improved solvent resistance and higher glass transition temperatures. The poly(arylene ethers) containing pendant amines were also reacted with an epoxy resin and 4,4'-diaminodiphenylsulfone to afford epoxy networks which had significant improvement in fracture toughness at selected compositions. Bis(o-aminophenol) monomers were investigated as precursors to poly(arylene ethers) having pendant amines by copolymerization with 4,4'-dichlorodiphenylsulfone and bisphenol-A. These studies resulted in insoluble gels, which suggested that reaction of both the o-aromatic amine and the phenolate with the activated dinalide was occurring. This was further confirmed by the successful oligomerization of o-aminophenol itself with 4,4'-dichloro diphenylsulfone, which afforded NMP soluble novel poly(sec-amino phenoxy diphenylsulfones) with high glass transition temperatures (Tg~276°C). / Ph. D.

Methods are presented to acquire data from analytical ultracentrifugation experiments by computer using the absorption optical scanning system of the Beckman Model-E ultracentrifuge. A computer program was written which analyzes sedimentation velocity experiments by the van Holde - Weischet method and by the second moment method. The van Holde - Weischet method allows a high resolution analysis of sedimentation velocity data by eliminating the effects of diffusion on the shape of the moving boundary to provide sedimentation coefficients for a heterogeneous composition of a sample. The second moment method obtains the sedimentation coefficient by calculating the second moment point, by which the sedimentation coefficient is defined. Since it is impractical to manually analyze sedimentation velocity data by this method, these computer programs make an important analysis method available to the researcher. Using this computer program, it is now possible to analyze data to a higher resolution and accuracy than manual analysis of stripchart recordings would permit. Moreover, the time required for the analysis is greatly reduced. Data from sedimentation equilibrium experiments are analyzed by x² minimization. Further, a program was written for the acquisition of data to measure diffusion coefficients from quasi elastic light scattering experiments with a Langley Ford correlator. The analysis of autocorrelation spectra from light scattering experiments is performed by the Levenberg - Marquardt method, which allows fitting of data to nonlinear models. The model used allows the analysis of multicomponent systems by fitting to a sum of exponentials and a baseline. Traditional analysis of autocorrelation data by hand was limited to least squares fitting of the data to a linear model of one component without an optimized baseline, often an unrealistic approximation of the system. Analysis of autocorrelation data by nonlinear curve fitting increases both the accuracy and amount of data that can be analyzed. The development of the PPOL-1 208-n series of plasmids and of the miniplasmid pMX is described. These plasmids were designed to allow studies of in vitro transcription and chromatin structure after reconstitution with histones. The plasmids themselves were analyzed by sedimentation and diffusion studies using the computer programs. Sedimentation data is presented which suggests a new method for rapid estimation of S₀ (the sedimentation coefficient at zero concentration) for molecules which show a concentration dependency of the sedimentation coefficient. This is accomplished by linearly extrapolating van Holde Weischet distributions to zero concentration. Manual analysis of sedimentation velocity experiments to determine nonideality contributions required several experiments, computer analysis can provide this information in a single experiment due to the increased resolution of the method. Diffusion data for this plasmid DNA is used to demonstrate the feasibility of the multicomponent analysis presented here. Also, sedimentation measurements were carried out on reconstituted chromatin and on the effects of ethidium bromide on reconstituted chromatin. The programs were used to demonstrate significant changes in chromatin structure upon ethidium bromide binding. These changes involved the reduction of S of reconstituted plasmids upon addition of ethidium bromide as well as a reduction of heterogeneity of the sample. The data indicates the possibility of a forced exchange of nucleosomes between plasmids, as well as conformational changes in the chromatin structure. / Graduation date: 1993

No description available.

Dissertation (PhD)--Stellenbosch University, 2004 / ENGLISH ABSTRACT: Over the past decade peptide bola-amphiphiles have been the subject of much attention because of their role as potential models of functionalised membranes and as new generation surfactants. In the quest for new surfactants a peptidomimetic-based approach was used to design a library of novel 'hybrid' bola-amphiphilic peptide surfactants derived from sapecin B and a model symmetrical oligo-glycine bola-amphiphile. The library was divided into different series, each one purpose-built; first, to investigate hierarchal supramolecular architecture and, second, to investigate potential antimicrobial activity. The bola-amphiphiles were synthesised using Fmoc-polyamide based solid phase peptide synthesis and purified via high performance liquid chromatography. The peptide hybrids were characterised using electro spray mass spectrometry, nuclear magnetic resonance, different modes of electron microscopy, Fourier-transform infrared spectroscopy and, in some cases, further studies were done using circular dichroism and bioactivity tests. The model bola-amphiphile suberamide(GGh was synthesised using peptide fragment condensation based on solid phase peptide synthesis. The synthesis is bi-directional (N~C and C~N) and versatile, making it possible to synthesis new dicarboxylic oligopeptide bola-amphiphiles and other analogous compounds. The product, suberarnide(GG)2, was purified using its inherent ability to self-assemble in an acidic solution. Novel asymmetrical bola-amphiphiles composed of dipeptide head groups linked via an aliphatic (I)-amino acid, serving as a hydrocarbon spacer, were also synthesized. Two small libraries of bola-amphiphiles were established - the first involved variation in to-amino acid length and the other variation in the C-terminal amino acid. The bolaamphiphiles were self-assembled in either 0.1% trif1uoroacetic acid or 0.1% triethylamine. Electron microscopy revealed the formation of a variety of higher order supramolecular architectures based on ~-sheet self-assembly. FT-IR spectrometry indicated that interlayer and intralayer hydrogen bond networks, together with strong selfassociation, promoted by the hydrophobic effect and, in certain instances, electrostatic interactions, are responsible for the variety of supramolecular architectures. Variations in the higher order structures can be attributed to amino acid composition, specifically length of m-amino acid, nature of the C-terminal amino acid and the optimised solvent conditions used for the self-assembly process. A third library of novel 'hybrid' bola-amphiphilic peptide surfactants, in which a cationic tripeptide motif from antimicrobial peptides was combined in a hybrid molecule containing a oi-amino acid residue, was established. These bola-amphiphiles displayed potent antimicrobial activity against both Gram-positive and Gram-negative bacteria; the analogues were as active or more active than the leader peptides yet, remarkably, displayed little or no appreciable haemolytic activity. These organopeptide bolaamphiphiles thus demonstrated selective toxicity towards bacteria. The hydrophobicity imparted by the co-amino acid has contrasting effects on haemolysis and antimicrobial activity of the peptide analogues. The other unique feature of these peptides and their analogues is the fact they self-assembled into complex supramolecular architectures, composed primarily of ~-sheets. Their self-assembly is primarily governed by hydrophobic interactions together with inter and intralayer hydrogen bonding. Electron microscopy clearly revealed higher order structures for both peptides and analogues. The generation of higher order supramolecular architecture is dependent on optimisation of ~- sheet self-assembly whereas antimicrobial activity is dependent on the balance between net positive charge and optimum hydrophobicity of the peptide hybrids. This study has demonstrated that it is possible to design hybrid peptide surfactants capable of producing higher order supramolecular architecture and improving the antimicrobial activity whilst reducing the haemolytic effect. The study and design of these versatile 'purpose-built' bio-inspired surfactants heralds a novel approach, one that shows tremendous potential. / AFRIKAANSE OPSOMMING: Die afgelope dekade het bola-amfifiliese peptiede baie aandag geniet weens hulle rolle as potensiële modelle van gefunksionaliseerde membrane en as 'n nuwe generasie surfaktante. In die soeke na nuwe surfaktante is 'n peptiedornimetiese benadering gevolg om 'n biblioteek van nuwe "hibried" bola-amfifiliese peptiedsurfaktante van sapesien B en 'n simmetriese oligoglisien bola-amfifil af te lei. Die biblioteek is in verskillende reekse onderverdeel. Elke reeks is doelmatig vervaardig om ondersoek in te stel na twee aspekte, nl. die rangorde van die supramolekulêre strukture en die potensiële antirnikrobiese aktiwiteit. Fmoc-poliamied gebaseerde soliedefase-peptied-sin-tese is aangewend vir die sintese van die bola-amfifile en hulle is met behulp van hoë doeltreffendheid vloeistofchromatografie gesuiwer. Die peptiedhibriede is gekarakteriseer met behulp van elekrosproei massaspektrometrie, kern-magnetiese resonansie, verskillende modusse elektronrnikroskopie, Fourier-transform infrarooispektrometrie en, in sommige gevalle is verdere studies met sirkulêre dichroïsme en bioaktiwiteitstoetsing uitgevoer. Die bola-amfifilsuberamiedtflfij--model is met behulp van peptiedfragment-konden-sasie gesintetiseer gegrond op soliedefase-peptiedsintese. Dit sintese vind in twee rigtings plaas (N~C en C~N) en is veelsydig aangesien dit die sintese van sowel nuwe dikar-boksielbola- amfifile as ander analoë verbindings moontlik maak. Die produk, suber-arnied(GG)2, is gesuiwer met behulp van die verbinding se inherente vermoë tot self-montering in suur oplossings. Nuwe assimetriese bola-amfifile, saamgestel uit dipeptiedkopgroepe, gekoppel via 'n alifatiese ro-aminosuur, wat as koolwaterstofspasieerder dien, is ook gesintetiseer. Twee klein bola-amfifilbiblioteke is saamgestel - die een het variasies in die ro-aminosuur se lengte omvat en die ander een variasies in die C-terrninale aminosuur. Selfmontering van die bola-amfifile het plaasgevind in of 0,1 % trifluorasynsuur Of 0,1 % trietielamien. Elektronrnikroskopie het die bestaan van 'n verskeidenheid hoërorde supramolekulêre strukture, gegrond op p-plaatselfmontering, aangetoon. Uit FT-IR-spektrometrie blyk dit dat inter - en intralaag waterstofbinbdingsnetwerke en sterk selfassosiasie, 19. word bevorder deur die hidrofobiese effek en, in sekere gevalle, elektrostatiese interaksies, is verantwoordelik vir die verskeidenheid supramolekulêre strukture. Variasies in die hoërorde strukture kan toegeskryf word aan aminosuursamestelling, in besonder die lengte van die ro-aminosuur, die aard van die C-terminale aminosuur en die geoptimiseerde oplosmiddelkondisies wat gebruik is vir die selfmonteringsproses. 'n Derde biblioteek nuwe "hibried" bola-amfifiliese peptiedsurfaktante, waarin 'n kationiese tripeptiedmotief uit antimikrobiale peptiede gekombineer is met 'n m-aminosuurresidu, is geskep. Sommige van hierdie bola-amfifile het 'n kragtige antimikrobiese aktiwiteit teenoor sowel Gram-positiewe as Gram-negatiewe bakterieë gertoon. Die analoë strukture was aktief, of selfs meer aktief as die voorste peptiede maar het, verbasend genoeg, nie 'n beduidende hemolitiese aktiwiteit vertoon nie. Hierdie organopeptied bola-amfifil het dus 'n selektiewe toksisiteit teenoor bakterieë vertoon. Die hidrofo-bisiteit, as gevolg van die ui-aminosuur, het 'n resiproke effek op hemolise en die antimikrobiese aktiwiteit van die peptiedanaloë. Die ander uitstaande kenmerk van die peptiede en hulle analoë is die vermoë om te selfmonteer en komplekse supramolekulêre strukture, bestaande hoofsaaklik uit ~-plate, te vorm. Hierdie selfmontering word in hoofsaak beheer deur hidrofobiese interaksies asook inter - en intralaagwaterstofbinding. Elektronmikroskopie het duidelik hoërorde strukture getoon by sowel dié peptiede as hulle analoë. Die ontwikkeling van hoërorde supramolekulêre struktuurvorms is afhanklik van die optimalisering van die ~-plaatselfmontering. Daarteenoor is die antimikro-biese aktiwiteit afhanklik van die balans tussen die netto positiewe lading en die opti-male hidrofobisiteit van die peptiedhibriede. Hierdie studie het getoon dat dit moontlik is om hibriedsurfaktante te ontwerp wat hoërorde supramolekulêre strukture te produseer en om die antimikrobiese aktiwiteit te verbeter terwyl die hemolitiese effek verminder word. Die studie en ontwerp van hier-die veeldoelige, "doelmatig-gesintetiseerde" biogeïnspireerde surfakante stel 'n unieke benadering daar, wat oor groot potensiaal beskik.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This study describes the synthesis and self-assembly of hetero-arm molecular brushes (hetero-arm MBs). These MBs consist of two polymeric side chains (SCs) of different natures, alternatingly distributed along the main chain (backbone). Two different types of hetero-arm MBs were prepared: first, alternating amphiphlic hetero-arm MBs (AMBs), and second, alternating hetero-arm MBs (AHMBs). Hetero-arm AMBs were synthesized via two strategies: (I) via a combination of “grafting through” and “grafting onto”, and (II) via “grafting through”. In approach (I), poly[vinyl benzyl (polyethylene glycol)-alt-N-alkyl-maleimide)] (poly[VB-(PEG12)-alt-N-(CnH2n+1)-MI]) was prepared via radical copolymerization of vinyl benzyl-terminated polyethylene glycol (VB-PEG12) with maleic anhydride (MAnh) (grafting through), which produces graft copolymers with PEG SCs and reactive succinic anhydride repeat units alternatingly distributed along the backbone. These graft copolymers were then modified by nucleophilic substitution (imidization) with alkyl amines (CnH2n+1-NH2) on the succinic anhydride residues (grafting onto). Three different primary amines possessing different alkyl chain lengths (n = 4, 12 and 16) were used in the modification process. In this way, hetero-arm AMBs with different hydrophilic to hydrophobic ratios were obtained. In approach (II), similar hetero-arm AMBs were prepared in a one-step grafting through approach. In this case, poly[VB-(PEG17)-alt-N-(CnH2n+1)-MI] (n = 10, 16 and 20) was prepared via radical copolymerization of VB-PEG17 with N-dodecylmaleimide, N-hexadecylmaleimide and N-icosylmaleimide. Following the synthesis step, self-assembly of these hetero-arm AMBs in arm-selective solvents was investigated in relation to the alkyl chain length. The morphology of the obtained assemblies was characterized by Field Emission gun-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Fluorescence Microscopy (a fluorescent dye was encapsulated). Cylindrical-like aggregates, length 10 μm and diameter ~ 250 nm, were obtained upon hetero-arm AMBs self-assembly. The second type of hetero-arm MBs was hetero-arm AHMBs, in which the SCs consist of PEG and poly(N,N-dimethylamino-ethyl methacrylate) (PDMAEMA). These hetero-arm AHMBs were prepared via a combination of grafting through and grafting from approaches. In this case, poly[vinyl benzyl-(polyethylene glycol)-alt-N-(poly(N,N-dimethylamino-ethyl methacrylate) maleimide] (poly[VB-(PEG17)-alt-N-(PDMAEMA)-MI) was prepared in the following steps: (1) alternating poly[vinyl benzyl-(polyethylene glycol)-alt-N-(4-hydroxyphenyl) maleimide] (poly[VB-(PEG17)-alt-N-(HPh)-MI]) was synthesized via radical copolymerization of VB-PEG17 with N-(4-hydroxyphenyl) maleimide (N-HPhMI). (grafting through), (2) the hydroxyl sites were esterified with 2-bromoisobutyryl bromide to afford poly [vinyl benzyl-(polyethylene glycol)-alt-N-(4-(2-bromobutyryloxy)phenyl) maleimide] (poly[VB-(PEG17)-alt-N-(BrPh)-MI]) (macroinitiator) and (3) an atom transfer radical polymerization (ATRP) reaction of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) was initiated from the obtained macroinitiator. This approach afforded poly[VB-(PEG17)-alt-N-(PDMAEMA)-MI] hetero-arm AHMBs with two water soluble SCs; however, one is water soluble at all pHs and temperatures (i.e. PEG), while the other is a pH- and temperature-sensitive polymer (i.e. PDMAEMA). Initial attempts were made to fabricate cylindrical organo/silica hybrid materials based on these AMHBs as the organic template and tetra-ethylorthosilicate as the silica precursor. Preliminary results indicate the formation of silica nano-wires, ~ 8 μm in length and ~45 nm in diameter. The self-assembly behavior of these AHMBs in water at a temperature above the lower critical solution temperature of PDMAEMA (> 55 °C) was also investigated. Fibril morphology (~ 30 nm in diameter) was observed. This study addresses initial attempts to fabricate organic/inorganic hybrid materials with controlled size and morphologies via densely grafted hetero-arm molecular brushes. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf die sintese en selfsamestelling van prototipe molekulêre borsels (prototipe MBs). Hierdie MBs bestaan uit twee polimeriese sykettings (SKs) van verskillende aard wat afwisselend langs die hoofketting (ruggraat) voorkom. Twee verskillende tipes van die prototipe MBs is gesintetiseer: eerstens, afwisselende amfifiliese prototipe MBs (AMBs), en tweedens, afwisselende hetero-arm prototipe MBs (AHMBs). Prototipe AMBs is gesintetiseer d.m.v. twee strategieë: (I) deur 'n kombinasie van „enting deur‟ en „enting aan‟ benaderings, en (II) deur middel van „n „enting deur‟ benadering. In benadering (I) is poli[vinielbensiel(poliëtileenglikol)-alt-N-alkiel-maleïenamied)] (poli[VB-(PEG12)-alt-N-(CnH2n+1)-MI]) gesintetiseer deur radikaalkopolimerisasie van vinielbensiel-beëindigde-poliëtileenglikol (VB-PEG12) met maleïenanhidried („enting deur‟) wat entkopolimere produseer met PEG SKs en reaktiewe suksienanhidried herhaaleenhede wat afwisselend langs die ruggraat versprei is. Daarna is die entkopolimere gewysig d.m.v. nukleofiliese substitusie (imiedisering) met alkielamiene (CnH2n+1-NH2) op die oorblywende suksienanhidried („enting op‟). Drie verskillende primêre amiene met verskillende alkielkettinglengtes (n = 4, 12 en 16) is gebruik vir die wysigingsproses. So is prototipe AMBs met verskillende hidrofiliese tot hidrofobiese verhoudings verkry. In benadering (II) is soortgelyke prototipe AMBs gesintetiseer in 'n een-stap „enting deur‟ benadering. In hierdie geval is poli[VB-(PEG17)-alt-N-(CnH2n+1)-MI] (n = 10, 16 en 20) gesintetiseer d.m.v. radikaalkopolimerisasie van VB-PEG17 met N-dodesiel maleïenamied, N-heksadesiel maleïenamied en N-ikosiel maleïenamied. Na afloop van die sintese stap is die selfsamestelling van hierdie prototipe AMBs in spesifieke oplosmiddels in verhouding tot die alkielkettinglengtes ondersoek. Die morfologie van die versamelings is gekarakteriseer deur veld-emissie-geweer-(Eng: field emission gun-)-skandeerelektronmikroskopie (FE-SEM), transmissie-elektronmikroskopie (TEM) en fluoresserende mikroskopie („n fluoresserende kleurstof is ingesluit). Silinderagtige versamelings (lengtes ~10 μm en deursnee ~250 nm) is deur die selfsamestelling van prototipe AMBs verkry. Die tweede soort prototipe MBs is prototipe AHMB, waarin die SKs uit PEG en poli(N,N-dimetielaminoetiel metakrilaat) (PDMAEMA) bestaan. Hierdie prototipe AHMBs is d.m.v. 'n kombinasie van „enting deur‟ en „enting van‟ benaderings gesintetiseer. In hierdie geval is poli[vinielbensiel-(poliëtileenglikol)-alt-N-(poli(N,N-dimetielaminoetiel metakrilaat) maleïenamied] (poli[VB-(PEG17)-alt-N-(PDMAEMA)-MI) gesintetiseer deur van die volgende stappe gebruik te maak: (1) sintese van afwisselende poli[vinielbensiel-(poliëtileenglikol)-alt-N-(4-hidroksifeniel) maleïenamied] (poli[VB-(PEG17)-alt-N-(HPh) -MI) deur midel van radikaalkopolimerisasie van VB-PEG17 met N-(4-hidroksifeniel) maleïenamied (N-HPhMI) („enting deur‟), (2) esterifikasie van die hidroksielgroepe met 2-bromoisobutiriel bromied om poli[vinielbensiel-(poliëtileenglikol)-alt-N-(4-(2-bromobutirieloksi) feniel) maleïenamied] (poli[VB-(PEG17)-alt-N-(BrPh)-MI]) (makro-afsetter) te berei, en (3) die atoomoordrag-radikaalpolimerisasie reaksie van 2-(N,N-dimetielamino)etiel metakrilaat (DMAEMA) wat begin is vanaf die gevormde makro-afsetter. Hierdie benadering gee poli[VB-(PEG17)-alt-N-(PDMAEMA)-MI] prototipe AHMBs met twee wateroplosbare SKs, waarvan een wateroplosbaar is by alle pHs en temperature (d.w.s. PEG), terwyl die ander tipe SK „n pH- en temperatuur-sensitiewe polimeer is (d.w.s. PDMAEMA). Aanvanklike pogings is aangewend om silindriese organo/silika hibriedmateriale te sintetiseer, gebaseer op hierdie AHMBs as die organiese segment en tetraëtielortosilikaat as die silika voorloper. Die voorlopige resultate dui op die vorming van silikananodrade, lengte ~8 μm en deursnit ~45 nm. Die selfsamestellingsgedrag van hierdie AHMBs is ook in water ondersoek by 'n temperatuur hoër as die laer kritieke oplossingstemperatuur van PDMAEMA (> 55 °C). „n Draadagtige morfologie (deursnit ~30 nm) is waargeneem. Hierdie studie beskryf aanvanklike pogings om organiese–anorganiese hibriedmateriale met beheerde groottes en morfologieë via dig-geënte hetero-arm molekulêre borsels te vervaardig.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The creation of nanometer-scale (nanoscale) materials has fascinated and inspired the scientific community for more than a quarter of a century because of the wide range of applications of these materials, e.g. applications in drug delivery, medicine, tissue engineering, memory storage, display and audio devices, semiconductors, etc. π-Conjugated dendrimers have a proposed flat packing arrangement. An alternating phenyl isoxazole dendrimer system was developed to investigate this phenomenon. The synthesis of this dendritic system was attempted by divergent and convergent approaches. Preparation of the second generation failed because some functional groups inhibited the monomers to react to the first generation. Other examples of nano materials that have attracted a vast amount of interest are the so-called discotic amphiphiles. Discotic amphiphilic molecules have the potential to self-assemble into helical architectures. Discotic systems bearing chiral polar side chains (one and three respectively) were developed. Their self-assembly was investigated in variable concentration and variable solvent composition experiments. These systems did show signs of aggregation in UV-vis and CD spectroscopy experiments. Thread-like helical structures were observed with transmission electron microscopy. / AFRIKAANSE OPSOMMING: Nanometer-skaal materiale inspireer en fassineer wetenskaplikes al vir meer as 25 jaar as gevolg van hulle wye verskeidenheid toepassings bv.: die vervoer van geneesmiddels, weefsel ontwerp, geheue stoorspasie, digitale skerms, klank toerusting, geleiers, ens. π-Gekonjugeerde dendrimere het 'n plat drie dimmensionele rangskikking. 'n Afwisselende feniel isoxazole dendrimer stelsel was ontwikkel om hierdie verskynsel te ondersoek. Die sintese van hierdie dendritiese stelsel is aangepak deur divergerende en konvergerende benaderings. Sintese van die tweede generasie het misluk omdat sommige funksionele groepe die monomere geïnhibeer het om te reageer met die eerste generasie. Ander interessante voorbeelde van nano materiale, is die sogenaamde skyfvormige amphiphiles. Skyfvormige amphiphiles het die potensiaal om spontaan te versamel in heliese strukture. Skyfvormige molekules met chirale polêre sykettings (een en drie onderskeidelik) is ontwikkel. Hulle potensiaal om spontaan te versamel is ondersoek met wisselende konsentrasie en wisselende oplosmiddel samestelling eksperimente. Hierdie stelsels het tekens van versameling gewys in UV-vis en CD-spektroskopiese eksperimente. Staaf-vormige heliese strukture is waargeneem met transmissie-elektronmikroskopie.