Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Multiphase copolymers generally consist of copolymers where the disparate natures of each of the segments results in complex phase-segregated morphologies in the solid state. The outstanding properties and wide range of applications of multiphase copolymers has led to the need for more sophisticated synthesis methods to produce copolymers with controlled structures. Associated with developments in synthetic methods is the need to develop suitable techniques to characterize these materials in order to obtain a better understanding of their structure–property relationships. The synthesis of multiphase copolymers presents many challenges. These are related to the nature of the molecular requirements, were the monomers of each of the different components may not be polymerized by all available polymerization techniques. This has led to the need to combine different polymerization techniques to overcome such limitations. The focus of this study is the combination of living controlled polymerization techniques, namely anionic polymerization and RAFT polymerization, with hydroboration/autoxidation, to produce non-polyolefin block and graft copolymers. Block copolymers were synthesized by coupling anionic polymerization and hydroboration/autoxidation reactions. The first block segment was prepared via anionic polymerization, and then end-functionalized with a suitable functional group (e.g. an allyl group). A hydroboration/autoxidation reaction was then used to initiate the polymerization of the second block by the slow addition of oxygen at room temperature. Graft copolymers were synthesized using the 'grafting from' technique, by coupling RAFT copolymerization with hydroboration/autoxidation reactions. The backbone polymer was synthesized via RAFT copolymerization of symmetric and asymmetric monomer, after which a hydroboration/autoxidation reaction was carried out to produce graft copolymers. The hydroboration/hydroxylation reaction could also be used to modify an unsaturated polymer chain. The EPDM rubber chain was modified by transforming the double bond into an hydroxyl group, which could undergo an esterification reaction with an acid chloride RAFT agent to produce the multifunctional RAFT polymer. This was used for the controlled living free radical polymerization of the graft chains. Significant amounts of homopolymerization in addition to graft formation were obtained. Solid state NMR (SS NMR) and positron annihilation lifetime spectroscopy were used to determine the compositional phase segregation point in the graft copolymers. The spin diffusion data from the SS NMR provided insight into the seemingly anomalous positron data at the phase segregation point. It is demonstrated how these two techniques can provide complimentary data on the solid state morphology of these multiphase materials. / AFRIKAANSE OPSOMMING: In die algemeen bestaan multifase kopolimere uit segmente van verskillende aard wat komplekse fase-geskeide-morfologie in die vastetoestand tot gevolg het. Die uitstekende eienskappe en wye reeks toepassings van multifase kopolimere het daartoe gelei dat meer gesofistikeerde sintesemetodes vir die bereiding van kopolimere met gekontrolleerde strukture nodig was. Gepaardgaande met verwante ontwikkelings op die gebied van sintesemetodes was dit nodig om gepaste analitiese tegnieke te ontwikkel vir die karakterisering van hierdie verbindings, ten einde die struktuur–eienskap verwantskap van hierdie materiale beter te verstaan. Daar is egter baie uitdagings m.b.t. die sintese van hierdie multifase kopolimere. Dit is afhanklik van die aard van die molekulêre vereistes waar die monomere van elk van die verskillende komponente nie deur alle beskikbare polimerisasietegnieke gepolimeriseer kan word nie. Dit het daartoe gelei dat verskillende polimerasietegnieke gekombineer is ten einde hierdie beperkinge te oorbrug. Die fokus van hierdie studie is die kombinering van lewende vry-radikaal gekontrolleerde polimerisasietegnieke, naamlik anioniese polimerisasie en RAFTpolimerisasie, met hidroborering/outoksidasie, om nie-olefiniese blok- en entkopolimere te berei. Blok-kopolimere is berei deur die koppeling van anioniese polimerisasie en hidroborering/outoksidasie reaksies. Die eerste bloksegment is berei via anioniese polimerisasie en daarna is endfunksionering met 'n geskikte funksionele groep (bv. 'n allielgroep) bewerkstellig. Daarna is 'n hidroborering/outoksidasie reaksie gebruik om die polimerisasie van die tweede blok te inisieer d.m.v. die stadige toevoeging van suurstof by kamertemperatuur. Entkopolimere is berei deur gebruik te maak van die 'ent-vanaf' tegniek, d.m.v. die koppeling van RAFT-kopolimerisasie met hidroborering/outoksidasie reaksies. Die rugraatpolimeer is berei d.m.v. kopolimerisasie van simmetriese en nie-simmetriese monomere waarna die hidroborering/outoksidasie reaksie uitgevoer is om sodoende entkopolimere te vorm. Die hidroborering/hidroksilasie reaksie kon ook gebruik word om 'n onversadigde polimeerketting te wysig. Die EPDM rubberketting is gewysig deur die omskakeling van die dubbelbinding in 'n hidroksielgroep, wat dan 'n esterifikasie reaskie kon ondergaan met 'n suurchloried-RAFT verbinding, om sodoende die multifunksionele RAFT-polimeer te vorm. Dit is gebruik vir die gekontrolleerde lewende vry-radikaalpolimerisasie van die entkettings. Behalwe entvorming is 'n hoë mate van homopolimerisasie waargeneem. Vastetoestand KMR (VS KMR) en positronvernietigingsleeftydspektroskopie is gebruik om die saamgestelde faseskeidingspunt in die entkopolimere te bepaal. Die spindifffusie data van VS KMR het insig verleen aan die oënskynlik onreëlmatige positrondata by die faseskeidingspunt. In die studie is bewys hoe hierdie twee tegnieke komplimentêre data kan lewer m.b.t. die vastetoestandmorfologie van hierdie multifase materiale.

Thesis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: See fulltext for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Please refer to fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The high-resolution 195Pt NMR signals (128.8 MHz) of most of the octahedral mixed-ligand Pt(IV) complexes in the series [PtCl6-n(OH)n]2-, n = 0-6, have been recorded in aqueous solutions at 293 K. These signals show characteristic 35/37Cl isotope-induced fine structure that results from the presence of several isotopologues in samples with a natural chlorine isotope distribution; each 37Cl isotope incorporated into the Pt coordination sphere of one of these complexes affords a fixed upfield (low frequency) isotope shift of between 0.17 and 0.22 ppm, depending on the particular complex. This assignment is confirmed by the excellent agreement between the natural abundances of the various isotopologues and the relative contributions of the corresponding signals to the overall area of the experimental spectrum of the particular isotoplogue set, obtained by a non-linear least-squares line fitting procedure. These results confirm that the 195Pt magnetic shielding in isotopomers differing only in the combination of the two chlorine isotopes coordinated in sites trans to hydroxido-ligands are indistinguishable under these experimental conditions, unlike those of similar isotopomers in the related series of aqua-complexes [PtCln(H2O)6-n]4-n, n = 3-5, as reported by Koch and co-workers. Moreover, the order of 195Pt shielding for the members of all stereoisomer pairs in the series of hydroxido-complexes is the reverse of that reported for the corresponding pairs in the aqua-series. These and other observations are interpreted qualitatively in terms of the relative strengths of the trans-influences of aqua-, hydroxido- and chlorido-ligands and the effect of these on bond displacements in these complexes. The 195Pt NMR spectra of especially the complexes cis-[PtCl2(OH)4]2- and [PtCl(OH)5]2- show remarkable fine structure in a ca. 45 % 18O-enriched aqueous solution; apart from additional signals resulting from 18O-containing isotopologues, the resonance signals of isotopomers differing in the combination of 16/18O isotopes in sites trans to chlorido-ligands are partially resolved. The effect of temperature on the 35/37Cl isotope-induced fine structure in the 195Pt signals of [PtCl6]2- and [PtCl(OH)5]2- was investigated in the range 283-308 K; some interesting differences are observed. 195Pt relaxation time measurements for [PtCl6]2- in this temperature range reveal that line-broadening is at least partially responsible for the loss of resolution between the signals of isotopologues of this complex as the temperature is increased, possibly due to the spin-rotation relaxation mechanism. The temperature coefficient of 195Pt shielding and the magnitude of isotope shifts in the spectra of the complexes in this series show interesting correlations with the 195Pt shielding itself; an interpretation of these observations is presented. / AFRIKAANSE OPSOMMING: Die hoëresolusie 195Pt NMR seine (128.8 MHz) van die oktaëdriese gemengde-ligand Pt(IV) komplekse in die reeks [PtCl6-n(OH)n]2- is waargeneem in waterige oplossing by ʼn temperatuur van 293 K. Hierdie seine toon ʼn karakteristieke 35/37Cl isotoop-geïnduseerde fynstruktuur as gevolg van die teenwoordigheid van verskeie isotopoloë in monsters met ʼn natuurlike chloor isotoopverspreiding. Die verplasing van ʼn 35Cl isotoop deur ʼn 37Cl isotoop in die Pt koördinasiesfeer van hierdie komplekse lei tot ʼn laefrekwensie isotoopverskuiwing van die 195Pt resonansiesein van tussen 0.17 en 0.22 ppm, afhangend van die spesifieke kompleks. Die toekenning van resonansieseine in hierdie spektra word ondersteun deur die goeie ooreenstemming tussen die berekende natuurlike verspreiding van isotopoloë en die persentasie area bydrae van die ooreenstemmende pieke tot die area van volledige stel seine van die chemiese spesie, soos bepaal deur ʼn nie-linieêre kleinste-kwadrate passingsmetode. Hierdie resultate bevestig dat vir isotopomere waarvan slegs die kombinasie van chloorisotope wat in posisies trans tot hidroksido-ligande gekoördineer is ʼn ononderskeibare 195Pt magnetiese skerming waargeneem word, m.a.w. ʼn enkele resonansiesein word vir hierdie isotopomere gemeet, anders as gerapporteer deur Koch en medewerkers vir die verwante aqua-komplekse [PtCln(H2O)6-n]4-n waar n = 3-5. Verder is die order van 195Pt magnetiese skerming vir stereoisomere in hierdie hidroksido-komplekse in elke stereoisomer paar die teenoorgestelde van dit waargeneem vir die ooreenstemmende aqua-komplekse. Hierdie waarnemings word kwalitatief geïnterpreteer in terme van die verskillende trans-invloede van die chlorido-, aqua- en hidroksido-ligande en die effekte daarvan op bindingslengtes in die komplekse. In ʼn ongeveer 45 % 18O-verrykte monster toon die 195Pt seine van veral die komplekse cis-[PtCl2(OH)4]2- en [PtCl(OH)5]2- uitsonderlike fynstruktuur vanweë die addisionele seine van 18O-bevattende isotopoloë en die parsiële resolusie van die seine van isotopomere wat verskil in die kombinasie van 16/18O isotope wat trans tot chlorido-ligande gekoördineer is. ʼn Studie is gemaak van die uitwerking van temperatuur op die 35/37Cl isotoop-geïnduseerde fynstruktuur in die 195Pt seine van die komplekse [PtCl6]2- en [PtCl(OH)5]2- in die gebied 283-308 K; interessante verskille is waargeneem. 195Pt magnetiese relaksasietyd metings vir die kompleks [PtCl6]2- in waterige oplossing in hierdie temperatuurgebied toon dat verbreeding van resonansieseine ten minste gedeeltelik verantwoordelik is vir die waargenome verlies aan resolusie tussen die seine van isotopoloë namate die temperatuur styg; die verbreeding van seine kan waarskynlik aan die spin-rotasie relaksasiemeganisme toegeskryf word. Die temperatuurkoëffisiënt van 195Pt magnetiese skerming en die grootheid van isotoopverskuiwings in die spektra van die hidroksido-komplekse in hierdie reeks toon interessante korrelasies tot die 195Pt magnetiese skerming; ʼn interpretasie van hierdie waarnemings word voorgestel.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Please refer to full text for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Indirect nuclear spin-spin coupling constants in high resolution nuclear magnetic resonance (NMR) spectroscopy provide the most powerful method for determining conformations and structures of molecules in solution. The research described in this dissertation establishes the conformational and substituent dependencies of several new types of nuclear spin-spin coupling for use in structural studies. It was also of interest to determine the electronic factors which lead to the observed experimental trends. Geminal, vicinal, and four-bond carbon-carbon nuclear magnetic resonance coupling constants were studied experimentally with fifty carbon-13 enriched alicyclic compounds. Because of the small magnitudes of many of these coupling constants it ~vas necessary to modify existing Fourier transform NMR equipment to perform J-resolved two-dimensional NMR experiments. With the greater spectral resolution it was possible to determine 56 intercarbon geminal (²J(cc)), 107 vicinal (³J(cc)) and 26 four-bond (⁴J(cc)) coupling constants. These data represent the largest collection of ²J(cc), the only known data for ⁴J(cc), and the most accurate compilation of vicinal ¹³C-¹³C coupling constants. In combination with molecular orbital methods, the relevant conformational and substituent trends in each of these series were elucidated. Because of the great amount of interest in the importance of bridgehead interactions in "strained" molecules, a study is presented of coupling transmitted via nonbonded interactions between the bridgehead carbons in a series of l-substituted-bicycloalkanes. The two-dimensional Fourier transform methods were again used to obtain the experimental coupling constants and molecular orbital methods were used to determine the importance of the intercarbon bridgehead interactions on ¹H-¹H, ¹³c-¹H, ¹³C-¹³C, ¹³c-¹⁹F , and ¹H-¹⁹F coupling constants. In all cases the nonbonded interactions increased dramatically as the separation between the bridgehead carbons decreased. Further understanding of mechanisms of "through space" coupling were based on NMP. studies of the long range coupling constants (⁵J(HF) and ⁴J(HF)) in N-methyl-8-fluoroquinolinium halides. The X-ray structure of N-methyl-8-fluoroquinolinium chloride was determined in an attempt to calculate the observed ⁵J(HF) and ⁴J(HF). A selective population inversion mIR method was used to show that the sign of ⁵J(HF) in N-ethyl-8- fluoroquinolinium iodide is positive.

Carbon-13 nuclear magnetic resonance is a very useful spectroscopic technique in studying organic compounds, especially when the proton NMR does not provide much information. In this study of multicyclic lactams, different NMR techniques were used: broadband decoupled spectra, single-frequency off-resonance decoupling (SFORD), and the attached proton test (APT). Lanthanide shift reagents and lanthanide relaxation reagents were also used. Almost all the carbon-13 resonances of mono-, bi-, and polycyclolactams were unambiguously assigned. The most powerful method in the assignments was based on the use of the lanthanide induced shifts (LIS) which confirmed the assignments qualitatively and quantitatively. The quantitative confirmation comes from the calculations of LIS and their comparison with the observed shifts. The carbon-13 chemical shielding of the studied lactams was analyzed and compared with analogous compounds. The results presented provide a consistent picture and the major influences in the trends of the ¹³C chemical shifts. However, no empirical relationships were derived for this series of compounds. The solution conformations of most of these lactams have been investigated using the shifts induced in their carbon-13 NMR by Yb(dpm)₃. These conformations were compared with structures obtained from X-ray data and MINDO/3 calculations. The structural analyses of ε-caprolactam and 3-azabicyclo[4.3.1]decan-4-one showed that these molecules have at least two conformations in solution. The LIS structural analyses were confirmed by using ¹³C T₁ relaxation times in Gd(dpm)₃ and Gd(fod)₃ relaxation reagents. The different contributions to the ¹³C NMR lanthanide induced shifts (LIS) were studied with emphasis in determining the importance of the ligand pseudocontact contribution. This was found to be important, especially in carbons in proximity to the complexation site.

<p>The Application of Magnetic Resonance (MRI) and Computed Tomography Imaging (CT) in the Diagnosis and Management of Maxillofacial Tumours. For decades maxillofacial surgeons over the world have been frustrated by the high and often fatal recurrence of certain advanced jaw tumours. This study conclusively proves that Computed Tomography and especially Magnetic Resonance Imaging significantly decreases recurrence of Odontogenic Keratocyst and Ameloblastoma and allows surgical planning to avoid these recurrences.</p>

Proteins play an important role in cells, as the morphology, function and activities of the cell depend on the proteins they express. The key to understanding how different proteins function lies in an understanding of the molecular structure. The overall aim of this thesis was the determination of the structure of DWNN domains. This thesis described the preparation of samples of human DWNN suitable for structural analysis by nuclear magnetic resonance spectroscopy (NMR), as well as NMR analysis.