Thesis (MSc)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: Over the past two decades, field flow fractionation (FFF), as a polymer characterization technique, has
become cutting edge technology. The demand for molar mass and size characterisation of complex
polymer systems has increased, especially in cases where classical calibration techniques such as
size exclusion chromatography (SEC) has shown several shortcomings. FFF is a technique
resembling chromatography. It has several significant advantages over SEC, especially for the
characterisation of ultrahigh molar mass (UHMM), branched and gel-containing polymers. In this
study, polybutadienes, which often contain the abovementioned species, were analysed by SEC and
asymmetric flow field flow fractionation (AF4). Both separation techniques were coupled to refractive
index and multi-angle laser light scattering detection. Similarly, polyrotaxanes, which are polymers
with complex and unique molecular architectures, were also investigated. Results showed that AF4
can explicitly be used as a superior tool over SEC. In the case of UHMM polybutadienes, much higher
molar masses could be detected by AF4, due to the absence of shear degradation which is often
encountered in SEC. Gel-containing species could be detected by AF4 as no filtering is required prior
to injection. Abnormal retention behaviour, a phenomenon often encountered in UHMM branched
polymers, was observed in SEC analysis of the polyrotaxanes materials. AF4 provided sufficient
separation from low to high molar masses, without out any irregularities. / AFRIKAANSE OPSOMMING: Gedurende die afgelope twee dekades het veldvloeifraksionering (FFF) as ‘n
polimeerkarakteriseringstegniek groot veld gewen. Die aanvraag na molekulêre massa en groottekarakterisering
van komplekse polimeersisteme het toegeneem, veral in die gevalle waar klassieke
kalibrasietegnieke soos grootte-uitsluitingschromatografie (SEC) etlike tekortkominge getoon het. FFF
is ‘n tegniek soortgelyk aan chromatografie, en het voorheen bewys dat dit oor ‘n redelike aantal
voordele bo SEC beskik, veral in die geval van ultrahoë molekulêre massa- (UHMM-), vertakte- en jelbevattende
spesies. In die huidige studie is polibutadieenpolimere, wat dikwels bogenoemde spesies
bevat, geanaliseer met behulp van SEC en onsimmetriese vloei-veldvloeifraksionering (AF4). Beide
skeidingstegnieke is gekoppel aan ‘n brekingsindeks en multihoek-laserligverstrooiingsdetektors. Op
dieselfde wyse is polirotaksane (polyrotaxanes) met komplekse molekulêre argitektuur bestudeer.
Daar is bewys dat AF4 uitsluitlik gebruik kan word as ‘n meer geskikte tegniek bo SEC. Baie hoër
molekulêre massas kon deur middel van AF4 vir UHMM polibutadieenpolimere raakgesien word as
gevolg van die verminderde afbrekende degradasie wat dikwels voorkom met SEC. Jel-bevattende
spesies is suksesvol geïdentifiseer met behulp van AF4 waartydens geen filtrering vir analise nodig
was nie. Abnormale retensie was sigbaar tydens SEC analise van monsters van polirotaksane, wat
dikwels voorkom in vertakte polimere. In teenstelling het AF4 bewys dat ‘n bevredigende skeiding van klein na groot molekulêre massas, sonder enige tekortkominge, moontlik is.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/19997 |
| Date | 03 1900 |
| Creators | Makan, Ashwell Craig |
| Contributors | Pasch, H., 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 |
| Rights | Stellenbosch University |
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