Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:
Hybrid graft copolymers of polystyrene (PSty) and polydimethylsiloxane macromonomers (PDMS)
were synthesised. PSty-g-PDMS was synthesised employing the grafting through technique via a
conventionally free radical polymerization (FRP) using a polydimethylsiloxane macromonomer. In
this series the amount of PDMS incorporated into the copolymer was varied by varying the
macromonomer to styrene ratios as well as the length of the PDMS side chain. This allows for the
study of the effect that the macromonomer content and the branching length has on the efficiency
of the grafting process. A second series of PDMS-g-PSty was also synthesized where the PDMS
forms the backbone and the PSty the grafts. Two synthetic techniques were employed for the
formation of these polymers. Firstly, the grafting onto approach was used where functional
polystyrene prepolymers with either an allyl or vinyl end-groups were synthesised anionically
(living anionic polymerization) prior to the coupling of a functional prepolymer using a
hydrosilylation reaction with a Karstedt platinum catalyst. This technique was successful and gave
insight to the effect of the polystyrene prepolymer graft length has on the grafting efficiency as well
as the functional groups needed on the PDMS backbone. Furthermore, the effect of the viscosity
(of the PDMS macromonomer) plays on the grafting efficiency was also elucidated. Lastly, the
grafting from approach was employed for the formation of PDMS-g-PSty. ATRP, atom transfer
radical polymerization, of styrene using a bromoisobutyrate functional PDMS macroinitiator was
used for the synthesis of these copolymers. This was accomplished by reacting commercial silane
functional PDMS molecules via a hydrosilylation reaction (using a Karstedt catalyst) with allyl-2-
bromo-2-methyl-propionate to give a PDMS macroinitiator with bromoisobutyrate functional
groups. This will allow for the initiation and growth of polystyrene branches from the PDMS
backbone (employing ATRP with a suitable catalyst and ligand). The formation of the endproduct,
PDMS-g-PSty, via this route proved to be extremely difficult and largely unsuccessful.
Liquid chromatography (LC) at the critical point (LCCC) of polystyrene was used to separate the
graft material from homo-polymers which might have formed as well as from the PDMS
macromonomer. This technique allows for a very fast chromatographic analysis of the grafting
reaction. Under the critical conditions of PSty it was found that the graft copolymer eluted at a
lower retention time than the unreacted macromonomer and PSty homopolymer. Two-dimensional
chromatography, where LCCC (1st dimension) was coupled to size exclusion chromatography (2nd
dimension), was used for the evaluation of the CCD and MMD (molecular mass distribution) of the
graft material. LC was furthermore coupled off-line to FTIR and TEM using an LC interface. LCFTIR
gave insight to the microstructure of the material, whilst LC-TEM gave insight to the
morphological nanostructure of the material. / AFRIKAANSE OPSOMMING:
Hibried ent-kopolimere is gesintetiseer uit polistireen (PSty) en polidimetielsiloksaan (PDMS).
PSty-g-PDMS is gesintetiseer deur gebruik te maak van die ent-deur tegniek via ‘n konvensionele
vrye radikaal polimerisasie proses (VRP). In die reeks is die hoeveelheid PDMS wat geïnkorporeer
is, gevarieer deur die hoeveelheid PDMS tot PSty verhouding te verander asook die lengte van die
PDMS sytak. Gevolglik het dit toegelaat vir die studie van die effek wat die makromonomeer
inhoud, sowel as die taklengte het op die effektiwiteit van die ent-proses. ‘n Tweede reeks is ook
gesintetiseer, waar die PDMS die ruggraat vorm van die ko-polimeer, en die stireen die takke vorm
van die ko-polimeer. Dus is PDMS-g-PSty gesintetiseer. Twee sintetiese tegnieke is benut vir die
vorming van die kopolimere. In die eerste geval is daar van die ent-op tegniek gebruik gemaak
waar funksionele polistireen prepolimere met ‘n alliel of ‘n silaan end-groep gesintetiseer is deur
gebruik te maak van ‘n anioniese lewendige polimerisasie voor die koppeling van die PDMS
makromonomere deur ‘n hidrosililasie proses met ‘n Karstedt platinum katalisator. Die tegniek
was suksesvol en het in diepte insig gegee van die effek wat die molekulêre lengte van die
polistireen prepolimeer het op die effektiwiteit van die ent-proses, sowel as die minimum
hoeveelheid funksionele groepe wat teenwoordig moet wees op die PDMS ruggraat. Verder is die
effek wat die viskositeit (van die PDMS makromonomeer) op die ent-proses het, bekend gemaak.
Laastens is daar ook van die ent-vanaf tegniek gebruik gemaak vir die vorming van PDMS-g-PSty.
AORP, atoom oordrag radikale polimerisasie, van stireen, deur gebruik te maak van ‘n
bromoisobutiraat funksionele PDMS makro-inisieerder, is gebruik vir die sintese van die
kopolimere. Die makro-inisieerders is bekom deur gebruik te maak van kommersiële silaan
funksionele PDMS, en dit is gereageer deur middel van ‘n hidrosililasie proses met alliel-2-bromo-
2-metiel-propionaat. Dit het PDMS makroinisieerders tot gevolg gehad met bromoisobutiraat
funksionele groepe. Gevolglik kon stireen takke vanaf die PDMS ruggraat gegroei word deur
gebruik te maak van AORP met ‘n geskikte katalisator en ligand. Die vorming van die end-produk,
PDMS-g-PSty, deur middel van hierdie roete was onsuksesvol. Vloeistof chromatografie by die
kritiese punt van polistireen was gebruik om die ent-produk te skei van die homo-polimere en
PDMS makromonomeer. Gevolglik kon die chemiese samestelling van die ent-produk geëvalueer
word. Twee-dimensionele chromatografie, waar vloeistof chromatografie by die kritiese punt van
polistireen in die eerste vlak gekoppel was aan grootte uitsluitings chromatografie in die tweede
vlak, was benut om die chemiese komposisie sowel as die molekul re massa verdeling van die entproduk
te verkry. Verder was vloeistof chromatografie indirek aan Fourier-oordrag infrarooi en
transmissie elektron mikroskopie (TEM) gekoppel. Eergenoemde het insig gegee tot die
mikrostruktuur van die materiaal, terwyl laasgenoemde insig gegee het tot die morfologiese
nanostruktuur van die materiaal.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3182 |
| Date | 03 1900 |
| Creators | Sutherland, Aimee Celeste |
| Contributors | Mallon, Peter Edward, University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
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