Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Multiphase copolymers generally consist of copolymers where the disparate natures of each
of the segments results in complex phase-segregated morphologies in the solid state. The
outstanding properties and wide range of applications of multiphase copolymers has led to
the need for more sophisticated synthesis methods to produce copolymers with controlled
structures. Associated with developments in synthetic methods is the need to develop
suitable techniques to characterize these materials in order to obtain a better understanding
of their structure–property relationships.
The synthesis of multiphase copolymers presents many challenges. These are
related to the nature of the molecular requirements, were the monomers of each of the
different components may not be polymerized by all available polymerization techniques.
This has led to the need to combine different polymerization techniques to overcome such
limitations.
The focus of this study is the combination of living controlled polymerization
techniques, namely anionic polymerization and RAFT polymerization, with
hydroboration/autoxidation, to produce non-polyolefin block and graft copolymers. Block
copolymers were synthesized by coupling anionic polymerization and
hydroboration/autoxidation reactions. The first block segment was prepared via anionic
polymerization, and then end-functionalized with a suitable functional group (e.g. an allyl
group). A hydroboration/autoxidation reaction was then used to initiate the polymerization of
the second block by the slow addition of oxygen at room temperature.
Graft copolymers were synthesized using the 'grafting from' technique, by coupling
RAFT copolymerization with hydroboration/autoxidation reactions. The backbone polymer
was synthesized via RAFT copolymerization of symmetric and asymmetric monomer, after
which a hydroboration/autoxidation reaction was carried out to produce graft copolymers.
The hydroboration/hydroxylation reaction could also be used to modify an
unsaturated polymer chain. The EPDM rubber chain was modified by transforming the
double bond into an hydroxyl group, which could undergo an esterification reaction with an
acid chloride RAFT agent to produce the multifunctional RAFT polymer. This was used for
the controlled living free radical polymerization of the graft chains. Significant amounts of
homopolymerization in addition to graft formation were obtained.
Solid state NMR (SS NMR) and positron annihilation lifetime spectroscopy were used
to determine the compositional phase segregation point in the graft copolymers. The spin
diffusion data from the SS NMR provided insight into the seemingly anomalous positron data
at the phase segregation point. It is demonstrated how these two techniques can provide
complimentary data on the solid state morphology of these multiphase materials. / AFRIKAANSE OPSOMMING: In die algemeen bestaan multifase kopolimere uit segmente van verskillende aard wat
komplekse fase-geskeide-morfologie in die vastetoestand tot gevolg het. Die uitstekende
eienskappe en wye reeks toepassings van multifase kopolimere het daartoe gelei dat meer
gesofistikeerde sintesemetodes vir die bereiding van kopolimere met gekontrolleerde
strukture nodig was. Gepaardgaande met verwante ontwikkelings op die gebied van
sintesemetodes was dit nodig om gepaste analitiese tegnieke te ontwikkel vir die
karakterisering van hierdie verbindings, ten einde die struktuur–eienskap verwantskap van
hierdie materiale beter te verstaan.
Daar is egter baie uitdagings m.b.t. die sintese van hierdie multifase kopolimere. Dit
is afhanklik van die aard van die molekulêre vereistes waar die monomere van elk van die
verskillende komponente nie deur alle beskikbare polimerisasietegnieke gepolimeriseer kan
word nie. Dit het daartoe gelei dat verskillende polimerasietegnieke gekombineer is ten einde
hierdie beperkinge te oorbrug.
Die fokus van hierdie studie is die kombinering van lewende vry-radikaal
gekontrolleerde polimerisasietegnieke, naamlik anioniese polimerisasie en RAFTpolimerisasie,
met hidroborering/outoksidasie, om nie-olefiniese blok- en entkopolimere te
berei. Blok-kopolimere is berei deur die koppeling van anioniese polimerisasie en
hidroborering/outoksidasie reaksies. Die eerste bloksegment is berei via anioniese
polimerisasie en daarna is endfunksionering met 'n geskikte funksionele groep (bv. 'n
allielgroep) bewerkstellig. Daarna is 'n hidroborering/outoksidasie reaksie gebruik om die
polimerisasie van die tweede blok te inisieer d.m.v. die stadige toevoeging van suurstof by
kamertemperatuur.
Entkopolimere is berei deur gebruik te maak van die 'ent-vanaf' tegniek, d.m.v. die
koppeling van RAFT-kopolimerisasie met hidroborering/outoksidasie reaksies. Die
rugraatpolimeer is berei d.m.v. kopolimerisasie van simmetriese en nie-simmetriese
monomere waarna die hidroborering/outoksidasie reaksie uitgevoer is om sodoende
entkopolimere te vorm.
Die hidroborering/hidroksilasie reaksie kon ook gebruik word om 'n onversadigde
polimeerketting te wysig. Die EPDM rubberketting is gewysig deur die omskakeling van die
dubbelbinding in 'n hidroksielgroep, wat dan 'n esterifikasie reaskie kon ondergaan met 'n
suurchloried-RAFT verbinding, om sodoende die multifunksionele RAFT-polimeer te vorm.
Dit is gebruik vir die gekontrolleerde lewende vry-radikaalpolimerisasie van die entkettings.
Behalwe entvorming is 'n hoë mate van homopolimerisasie waargeneem.
Vastetoestand KMR (VS KMR) en positronvernietigingsleeftydspektroskopie is
gebruik om die saamgestelde faseskeidingspunt in die entkopolimere te bepaal. Die
spindifffusie data van VS KMR het insig verleen aan die oënskynlik onreëlmatige positrondata by die faseskeidingspunt. In die studie is bewys hoe hierdie twee tegnieke
komplimentêre data kan lewer m.b.t. die vastetoestandmorfologie van hierdie multifase
materiale.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/18003 |
| Date | 12 1900 |
| Creators | Elhrari, Wael K. S. |
| Contributors | Mallon, P. E., 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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