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Multidimensional separation of complex polymers according to microstructure
Thesis (PhD)--Stellenbosch University, 2014.
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| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2014
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| _version_ | 1867613873601773568 |
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| access_status_str | Open Access |
| author | Maiko, Khumo Gwendoline |
| author2 | Pasch, Harald |
| author_browse | Maiko, Khumo Gwendoline Pasch, Harald |
| author_facet | Pasch, Harald Maiko, Khumo Gwendoline |
| author_sort | Maiko, Khumo Gwendoline |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2014. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/86227 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:03.527Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/86227 Multidimensional separation of complex polymers according to microstructure Maiko, Khumo Gwendoline Pasch, Harald Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Liquid chromatography Polymers -- Separation Isotope effect UCTD Dissertations -- Polymer science Theses -- Polymer science Thesis (PhD)--Stellenbosch University, 2014. ENGLISH ABSTRACT: Complex polymer systems have multiple distributions with regard to molecular parameters such as molar mass, functionality, chemical composition, molecular architecture and microstructure. These distributions affect the properties of the polymers making it necessary to develop separation methods to be able to correlate structure to property. A single onedimensional chromatographic method is usually not sufficient to separate these complex polymers with respect to all the distributions. Hence, multidimensional liquid chromatography is necessary for the complete analysis of complex polymers using two or more chromatographic techniques before detection. In this work, two novel liquid chromatographic methods were developed to separate complex polymers according to microstructure. Comprehensive two-dimensional liquid chromatography (LC x LC) was carried out to observe the correlation between microstructure and molar mass. The separation according to microstructure was coupled to NMR (LC-NMR) to observe, identify and quantify the different microstructural components during chromatographic elution. The first chromatographic method separated hydrogenated and deuterated polystyrene homopolymers with respect to the isotope effect. For the LC x LC experiments, liquid chromatography at critical conditions (LCCC) was employed as the first dimension separating according to the isotope effect and size exclusion chromatography (SEC) as the second dimension separating according to molar mass. The LC x LC results of the blends showed that there was an improvement in isotopic separation with an increase in molar mass. The LCNMR coupling using both 1H and 2H NMR detection allowed for the identification of low molar mass blend components which were not sufficiently separated by liquid chromatography. The second chromatographic method separated stereoregular poly(methyl methacrylate)s (PMMAs) with respect to tacticity. The LC x LC experiments of stereoregular PMMAs utilised solvent gradient liquid chromatography as the first dimension to separate according to tacticity and size exclusion chromatography (SEC) as the second dimension to separate according to molar mass. The LC x LC results showed a change in the triad composition with elution of the stereoregular PMMAs with a slight influence of molar mass. The LC-NMR coupling allowed the observation of the triad composition during chromatographic elution. AFRIKAANSE OPSOMMING: Komplekse polimeriese sisteme het meervoudige verspreidings ten opsigte van molekulêre parameters, soos byvoorbeeld, molêre massa, funksionaliteit, chemiese samestelling, molekulêre argitektuur en mikrostruktuur. Hierdie verspreidings beïnvloed die eienskappe van die polimere en dus is dit nodig om skeidingsmetodes te ontwikkel ten einde polimeerstruktuur met polimeereienskappe te kan korreleer. ‘n Enkele een-dimensionele chromatografiese metode is gewoonlik nie voldoende om hierdie komplekse polimere te skei met betrekking tot al die verspreidings nie. Multidimensionele vloeistofchromatografie, met die insluiting van twee of meer chromatografiese tegnieke, is dus nodig om polimere te skei voor waarneming kan plaasvind. Twee nuwe chromatografiese metodes is ontwikkel om komplekse polimere volgens mikrostruktuur te skei. Twee-dimensionele vloeistofchromatografie (LC x LC) is uitgevoer ten einde die korrelasie tussen mikrostruktuur en molêre massa te ondersoek. Daarna is die skeiding wat op mikrostruktuur gebasseer is, gekoppel aan KMR (LC-KMR) om die verskillende mikrostrukturele komponente gedurende chromatografiese eluering waar te neem, te identifiseer en te kwantifiseer. Die eerste chromatografiese metode het die gehidrogeneerde en gedeutereerde polistireen geskei met betrekking tot die isotoopeffek. Hier het die LC x LC skeiding bestaan uit vloeistofchromatografie onder kritiese kondisies (LCCC) as die eerste dimensie, wat skeiding bewerkstellig het gebasseer op die isotoopeffek, en grootte-uitsluitingschromatografie (SEC) as die tweede dimensie, wat skeiding bewerkstellig het gebasseer op die molêre massa. Die LC x LC resultate van die vermengings het ‘n verbetering in isotopiese skeiding met ‘n toename in molêre massa getoon. Deur gebruik te maak van die LC-KMR koppeling, waar beide 1H en 2H KMR waarneming gebruik is, was dit moontlik om die lae-molêre-massakomponente van vermengings wat nie volledig d.m.v. LC geskei kon word nie, te identifiseer. Die tweede chromatografiese metode het stereoreëlmatige polimetielmetakrilate (PMMAs) m.b.t. taktisiteit geskei. Die LC x LC skeiding van stereoreëlmatige PMMAs het bestaan uit oplosmiddel -gradiënt-LC as eerste dimensie om volgens taktisiteit te skei, en SEC as tweede dimensie om volgens molêre massa te skei. Die LC x LC resultate het ‘n molêre massa afhanklikheid van stereoreëlmatige PMMAs op taktisiteit getoon. Die LC-KMR koppeling het dit moontlik gemaak om die triade-samestelling gedurende chromatografiese eluering waar te neem. Doctoral 2014-04-16T17:28:18Z 2014-04-16T17:28:18Z 2014-04 Thesis http://hdl.handle.net/10019.1/86227 en_ZA Stellenbosch University xxv, 91 p. : ill. (some col.) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Liquid chromatography Polymers -- Separation Isotope effect UCTD Dissertations -- Polymer science Theses -- Polymer science Maiko, Khumo Gwendoline Multidimensional separation of complex polymers according to microstructure |
| title | Multidimensional separation of complex polymers according to microstructure |
| title_full | Multidimensional separation of complex polymers according to microstructure |
| title_fullStr | Multidimensional separation of complex polymers according to microstructure |
| title_full_unstemmed | Multidimensional separation of complex polymers according to microstructure |
| title_short | Multidimensional separation of complex polymers according to microstructure |
| title_sort | multidimensional separation of complex polymers according to microstructure |
| topic | Liquid chromatography Polymers -- Separation Isotope effect UCTD Dissertations -- Polymer science Theses -- Polymer science |
| url | http://hdl.handle.net/10019.1/86227 |
| work_keys_str_mv | AT maikokhumogwendoline multidimensionalseparationofcomplexpolymersaccordingtomicrostructure |