Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The study focused on the analysis of a variety o f synthesised tailored copolymers.
During the investigation o f the samples new and innovative analytical techniques
were developed to be able to identify the presence of certain predicted or expected
copolymerisation products.
Emphasis was placed on the versatility of CRYSTAF as a method for the analysis of
semi-crystalline copolymers. Changes in the crystallisation temperature were used as
an indicator, while the type o f method, solvent and sample weight served as variables
in the system. The percentage comonomer content distribution for an unknown
sample was determined from the standard curve plotted with the aid o f copolymers
with known comonomer content.
Ethylene/higher a-olefin and propylene/higher a-olefm copolymers were synthesised
by means o f a metallocene precatalyst. In both cases, NMR spectroscopy, DSC, GPC,
and CRYSTAF were used as analytical tools. In the ethylene series it was shown that
the sample mixture was homogenous in the molar mass axis (GPC) but not in the
chemical composition axis (CRYSTAF) regarding the comonomer content. For the
propylene series, an increase in stereoerrors was observed by NMR and this was
correlated with crystallisation on heating a DSC for the range o f copolymers.
In the case where ethylene/methyl methacrylate block copolymers were synthesised
using metallocene precatalyst, novel detection and separation methods were used and
developed. This included the use o f CRYSTAF fitted with a carbonyl filter, high
temperature gradient HPLC and high temperature liquid chromatography under
critical conditions (LCCC). The last two techniques were the first where separation
could be achieved with samples only dissolving at high temperature. All previous
mentioned techniques, as well as the coupling of FTIR to GPC and high temperature
gradient HPLC via LC-Transform revealed that the samples consisted o f varying
ethylene and MMA block lengths. / AFRIKAANSE OPSOMMING: Die doelstelling van die navorsing was die analise van spesiaalvervaardigde
kopolimere. Nuwe analitiese tegnieke is vir die bevestiging van sekere voorgestelde
kopolimerisasie-produkte ontwikkel.
Klem is gelê op die veelsydigheid van CRYSTAF as ’n metode vir die analise van
gedeeltelik-kristallyne kopolimere. Veranderinge in die kristallisasie-temperature is
as respons gebruik, terwyl die metode van sintese, die oplosmiddel en die hoeveelheid
monster as veranderlikes in die sisteem beskou is. ‘n Standaardkurwe vir
komonomeerinhoud is opgestel met behulp van kopolimere met ‘n bekende
komonomeerinhoud. Hierdie kurwe is gebruik om die komonomeerinhoudsverspreiding
van onbekende monsters te bepaal.
Etileen/hoër a-olefien- en propileen/hoër a-olefien-kopolimere is met behulp van ‘n
metalloseen pre-katalis gesintetiseer. In beide gevalle is KMR spektroskopie, DSC,
GPC en CRYSTAF gebruik om die analises uit te uitvoer. Met verwysing na
komonomeerinhoud is daar in die geval van die etileenreeks bevind dat die
monstermengsel homogeen is met betrekking tot die molere massa, maar nie met
betrekking tot die chemiese samestelling nie. Vir die propileenreeks is ’n verhoging
in die stereofoute met behulp van KMR waargeneem. Dit is gekorrelleer met
kristallisasie weens verhitting tydens DSC-bepalings vir die reeks kopolimere.
In die geval van die sinteses van etileen/metielmetakrilaat-blokkopolimere met
metalloseen as pre-katalis, moes nuwe waamemings- en skeidingstegnieke ontwikkel
word. Dit het die gebruik van CRYSTAF met ’n karbonielfilter, hoetemperatuurgradient-
HPLC en hoë-temperatuurvloeistofchromatografie onder kritiese
toestande ingesluit. Laasgenoemde twee tegnieke het vir die eerste keer skeiding van
monsters wat net by hoe temperature oplos, moontlik gemaak. Bogenoemde tegnieke,
sowel as die koppeling van FTIR met GPC en hoë-temperatuur-gradient-HPLC via
LC-transformasie het getoon dat die monsters etileen- en MMA-blokke met
verskillende lengtes bevat het.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52890 |
| Date | 12 1900 |
| Creators | Graef, Sven Markus |
| Contributors | Pasch, H., Sanderson, R. D., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 171 p. : ill. (some col.) |
| Rights | Stellenbosch University |
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