Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Complex polymers are defined by their distributive properties with respect to molecular weight, chemical
composition, functionality and molecular topology. As a result, polymer properties are very frequently
determined not only by one of these entities but by the correlation of two or more distributions. Aliphatic
polyesters are industrially implemented in high performance coatings, paints and varnishes. However, it is
typically difficult to correlate the resulting properties with the synthesis parameters as these polymers vary in
reactivity and application properties. Copolyester synthesis by direct polyesterification is often assumed to
produce randomized products due to the mechanisms involved in stepwise polymerization. The formation of
cyclic products by intramolecular reactions of hydroxyl (OH) and carboxylic (COOH) functional groups, sidereactions
such as transesterification, alcoholysis, and ester-ester interchange allow even further
randomization, enabling a highly complex system. Therefore, in addition to molecular weight distribution,
polyesters exhibit chemical composition, functionality type as well as branching distributions, classifying them
as complex polymeric systems. The different methods of polymer chromatography in combination with
sophisticated spectrometry techniques are useful tools for enabling the full description of the molecular
heterogeneity of these complex polyesters. The present study entails method development of different
modes of chromatography and mass spectrometry along with their combination, to facilitate the analysis of
the various distributions of two model polyester systems, phthalic and maleic anhydride, respectively, in
combination with propylene glycol. Gradient HPLC analysis enabled an oligomeric separation based on
chemical composition of the respective anhydride/propylene glycol samples. Its off-line coupling to MALDITOF
MS and ESI-QTOF MS revealed the presence of several distributions of varying endgroup functionality
type and molecular weight distributions at different intervals throughout the polymerization. In addition, online
gradient HPLC x size exclusion chromatography (2D-LC) was conducted to obtain the dual chemical
composition-molecular weight (CCD-MWD) distribution. The combination of the different coupling techniques
provided the opportunity to a more in-depth analysis of the structure-property relationships. / AFRIKAANSE OPSOMMING: Komplekse polimere word gedefinieer deur hul verdelings eienskappe ten opsigte van molekulêre massa,
chemiese samestelling, funksionaliteit en molekulêre topologie. Gevolglik, word hul eienskappe dikwels
bepaal deur nie net een van hierdie entiteite nie, maar ‘n korrelasie van twee of meer verdelings. Alifatiese
poliësters word industrieel geϊmplimenteer in hoë werkverrigting bestrykings, verwe en politoere, dog is dit
tipies moeilik om die uiteinde eienskappe met die verwante sintese parameters te korrelleer, aangesien die
polimere varieer in reaktiviteit en toepassingseienskappe. Ko-poliëster sintese vanaf direkte poliësterivering
word dikwels aanvaar om willekeurige produkte op te lewer as gevolg van die meganismes wat betrokke is
tydens trapgroei polimerisasie. Die produsering van sikliese produkte weens intra-molekulêre reaksies van
hidroksiel(OH) en karboksiel (COOH) verwante funksionele groepe, newereaksies soos transverestering,
alkoholise en ester-ester verwisseling, het verdere ewekansigmaking tot gevolg wat ‘n hoog
gekomplekseerde sisteem tot gevolg het. Benewens die molekulere massa verdeling, vertoon poliësters
dus chemiese samestelling, funksionaliteit tipe so wel as vertakkings verdeling wat hul as komplekse
polimeer sisteme klassifiseer. Die verskillende metodes van polimeer chromatografie in kombinasie met
gesofistikeerde spektrometriese tegnieke dien as nuttige bronne vir die volledige beskrywing wat betref die
molekulêre heterogeniteit van komplekse poliesters. Die huidige studie stel metode ontwikkeling van
verskillende modus van chromatografie, massa spektrometrie sowel as hul aaneenvoeging bekend, om die
die verskillende verdelings van twee model poliester sisteme, ftaal- en maleϊensuuranhidried onderskeidelik
in kombinasie met propileenglikol, suksesvol te analiseer. Gradiënt hoë-druk vloeistof chromatografie
(HPLC) analise het ‘n oligomeriese skeiding, gebaseer op die chemiese samestelling van die verskeie
anhidried /propileenglikol monsters, opgelewer. Die nie-gekoppelde skakeling met matriks-assisteerdelaser/
desorpsie-ionisasie tyd-van-vlug (MALDI-TOF) en elektron-sproei-ionisasie kwadrupool-tyd-van-vlug
(ESI-QTOF) massa spektrometrie het die teenwoordigheid van verskeie verdelings van varieërende
endgroep funksionaliteit tipe en molekulêre verdelings by verskillende intervalle tydens die polimerisasie aan
die lig gebring. Gekoppelde skakeling van gradient HPLC en grootte uitsluitings chromatografie is ook uitgevoer om die tweedelige chemiese samestelling-molekulere massa verdeling te bepaal. Aaneenvoeging
van die verskeie skakelings tegnieke het die geleentheid gebied om ‘n deeglike studie van die struktuureienskappe
verhoudinge suksesvol uit te voer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80127 |
| Date | 03 1900 |
| Creators | Pretorius, Nadine Odette |
| Contributors | Pasch, H., McLeary, J. B., Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xv, 112 p. : ill. |
| Rights | Stellenbosch University |
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