Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Block copolymers are very interesting materials but they are quite complex. During polymer
synthesis only a certain amount of control can be enforced. As copolymers are made up of two
or more different homopolymer segments, and therefore have different end group possibilities,
varying block lengths and block sequences, they have complex structures and are therefore
difficult to analyse.
Different techniques exist by which polymers can be analysed to determine the
aforementioned distributions. In order to achieve a complete characterisation of a polymer
structure, it is best to first use a separation technique to fractionate the polymer into more
homogeneous fractions, and then use identification techniques to analyse these fractions.
Polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers were investigated using
liquid chromatography at the critical conditions (LCCC) of the copolymers' corresponding
homopolymers, two-dimensional liquid chromatography (2D-LC) and FTIR. The block
copolymers were analysed using the established LCCC of PS but it was found that even
though separation of PS homopolymer and copolymer was obtained, PS blocks of the
copolymers contributed to some extent to the retention of the PEO blocks.
Some of the block copolymer samples were fractionated at the established critical
conditions of PS. These fractions were qualitatively and quantitatively analysed using FTIR
spectroscopy. The settings for the 2D-LC analysis were established, using LCCC of PS as the
first dimension and as the second dimension SEC, using DMF as eluent. DMF was a suitable
solvent to be used for the second dimension because PS, PEO and PS-b-PEO exhibited good
solubility in this solvent. THF did not dissolve the block copolymers completely.
The same solvent system as used for LCCC of PS was used for LCCC of PEO, but the
critical conditions correspond to a different solvent composition. The block copolymers were
analysed using the established LCCC of PEO but it was found that even though separation of
PEO homopolymer and copolymer was obtained, the PEO blocks of the copolymers
contributed to some extent to the retention of the PS blocks. Some of the block copolymer
samples were fractionated at the established critical conditions of PEO. These fractions were
qualitatively and quantitatively analysed using FTIR spectroscopy. The settings for the 2D-LC
analysis were established, using LCCC of PEO as the first dimension and as the second
dimension SEC using DMF as eluent was used. Lastly, qualitative and quantitative analyses of
the block copolymers were carried out using FTIR spectroscopy. / AFRIKAANSE OPSOMMING: Alhoewel blokkopolimere baie interessante verbindings is, is hulle redelik ingewikkeld.
Gedurende die kopolimerisasiereaksie kan daar net 'n sekere mate van kontrole behaal word.
Aangesien kopolimere uit twee of meer homopolimeersegmente, met verskillende end-groep
moontlikhede, bloklengtes en blokvolgordes bestaan, is dit baie moeilik om hierdie verbindings
te analiseer.
Verskillende tegnieke kan gebruik word vir die analise van polimere en die bepaling van
bogenoemde verspreidings. Ten einde 'n polimeerstruktuur volledig te karakteriseer is die beste
manier om eers 'n skeidingstegniek te gebruik om die polimeer in meer homogene fraksies te
fraksioneer en dan daarna hierdie fraksies te analiseer.
Polistireen-blok-poli(etileenoksied) (PS-b-PEO) kopolimere is ondersoek deur gebruik te
maak van vloeistofchromatografie by kritiese kondisies (LCCC) van die kopolimeer se
ooreenkomstige homopolimere; twee-dimensionele vloeistofchromatografie (2D-LC) en FTIR.
Die blokkopolimere is gekarakteriseer deur gebuik te maak van bevestigde LCCC van PS. Daar
is egter gevind dat alhoewel skeiding van die PS homopolimeer en die kopolimeer behaal is, PS
blokke van die kopolimere in 'n mate bygedra het tot die retensie van die PEO blokke.
Sommige van die blok-kopolimeermonsters is gefraksioneer by die bepaalde kritiese
kondisies van PS. Hierdie fraksies is kwalitatief en kwantitatief geanaliseer deur gebruik te maak
van FTIR spektroskopie. Die stellings vir die 2D-LC analise is bepaal deur gebruik te maak van
LCCC van PS as die eerste dimensie en SEC as die tweede dimensie, met DMF as elueermiddel.
DMF was 'n geskikte oplosmiddel vir die tweede dimensie aangesien PS, PEO en PS-b-PEO
goed oplosbaar is daarin. Die blokkopolimere was nie volledig oplosbaar in THF nie.
Dieselfde oplosmiddelsisteem soos gebruik vir die LCCC van PS is gebruik vir die
LCCC van PEO, maar die kritiese kondisies stem ooreen met 'n ander oplosmiddelsamestelling.
Die blokkopolimere is geanaliseer deur gebruik te maak van die bevestigde LCCC van PEO,
maar daar is bevind dat alhoewel skeiding van die PEO homopolimeer en kopolimeer behaal is,
die PEO blokke van die kopolimere in 'n mate bygedra het tot die retensie van die PS blokke.
Sommige van die blokkopolimeermonsters is gefraksioneer by die bevestigde kritiese kondisies
van PEO. Hierdie fraksies is kwalitatief en kwantitatief geanaliseer deur gebruik te maak van
FTIR spektroskopie. Die stellings vir die 2D-LC analise is bepaal deur gebruik te maak van LCCC van PEO as die eerste dimensie en SEC as die tweede dimensie, met DMF as
elueermiddel. Laastens is kwalitatiewe en kwanitatiewe analises van die blokkopolimere m.b.v.
FTIR spektroskopie uitgevoer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17937 |
| Date | 12 1900 |
| Creators | Grabowsky, Monika Elvira |
| Contributors | Paschs, Harald, 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 | Unknown |
| Type | Thesis |
| Rights | Stellenbosch University |
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