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Click chemistry for the preparation of advanced macromolecular architectures

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:
Different click chemistry methods have been used together with Reversible Addition-
Fragmentation chain Transfer (RAFT) mediated polymerization to synthesize macromolecular
architectures.
A new leaving group for RAFT was introduced. This triazole leaving group allows for easy
conjugation of the RAFT agent to various substrates via the copperI catalyzed Huisgen 1,3-dipolar
cycloaddition reaction. Subsequently monomer can be polymerized onto the substrate using the RAFT
agent. This connects the polymer to the substrate via a hydrolytically stable 1,2,3-triazole.
The Mitsunobu reaction was used to chain-end functionalize polymers. The Mitsunobu
reaction allows for the substitution of primary and secondary alcohols with a nucleophile. The
modification of polymer chain-ends was done in two ways. Firstly, thiol-functional chain-ends were
used as the nucleophile in the Mitsunobu reaction using propargyl alcohol as the alcohol. This yielded
alkyne-functional polymers. Thiol chain-end functional polymers were obtained by the aminolysis of
polymers synthesized via RAFT. Secondly, alcohol-functional polymers were modified. In the case of
poly(vinylpyrrolidone), the RAFT group was hydrolyzed and alcohols were obtained. Hydroxyl
functional PEG was obtained commercially. The hydroxyl functionality was reacted in the Mitsunobu
reaction using hydrazoic acid (HN3) as the nucleophile. Azide chain end functional polymers were
obtained. These alkyne and azide chain end functional polymers were subsequently used in the
copperI catalyzed Huisgen 1,3-dipolar cycloaddition reaction.
Ultra Fast Hetero Diels-Alder click chemistry (UFHDA) was used to synthesizes norbornenelike
structures (substituted 2-thiabicyclo[2.2.1]hept-5-ene moieties). Norbornene-like structures can be
polymerized via Ring Opening Metathesis Polymerization (ROMP). Monomers were synthesized
using phenethyl(diethoxyphosphoryl)dithioformate and cyclopentadiene. Macromonomers were
obtained from the UFHDA of Polystyrene (PSTY) synthesized via RAFT, using
phenethyl(diethoxyphosphoryl) dithioformate as the RAFT agent, and cyclopentadiene or
cyclopentadienyl-terminated PEG as the dienes. The obtained (macro) monomers were homo- and copolymerized
using Ring Opening Metathesis Polymerization (ROMP). For the ROMP, four different
Grubbs type catalysts were tested.The ring-strain promoted Huisgen 1,3-dipolar cycloaddition reaction uses cyclooctynes as the
alkyne. The ring-strain in this molecule allows for a fast reaction at room temperature. This reaction is
potentially very interesting for biological applications because it doesn’t require the toxic copper
catalyst. In this work three routes towards cyclooctynes are investigated. PEG was chain end
functionalized with the obtained cyclooctyne derivatives.
Overall, click chemistry methodologies were applied to synthesize different macromolecular
architectures. Results include a new type of RAFT agent that allows for easy conjugation to substrates,
reaction methods for chain end modification of polymers, and the synthesis of new monomers and
polymers. / AFRIKAANSE OPSOMMING:
Verskillende kliek chemie metodes, tesame met Omkeerbare Addisie Fragmentasie ketting
Oordrag beheerde polimerisasie (OAFO), is gebruik vir die sintese van makromolekulêre argitekture.
ʼn Nuwe verlatende groep vir OAFO was bekend gestel. Die triazool verlatende groep bied
die moontlikheid vir gemaklike koppeling van die OAFO agente met ‘n verskeidenheid van substrate
via die koperI gekataliseerde Huisgen 1,3-dipolêre siklo-addisie reaksie. Gevolglik kan monomere
gepolimeriseer word op die substraat deur middel van die OAFO agent. Dit laat toe vir die koppeling
van die polimeer op die substraat via a hidrolitiese stabiele 1,2,3-triazool.
Die Mitsunobu reaksie was gebruik vir die funksionaliseering van die end groepe van die
polimeer ketting. Die Mitsunobu reaksie laat toe vir die substitusie van primêre en sekondêre alkohole
met ‘n nukleofiel. Die verandering van die polimeer ketting end groepe was uitgevoer op twee
verskillende maniere. Eerstens is ketting end groepe met ‘n tiol funktionaliteit gebruik as a nukleofiel
in die Mitsunobu reaksie deur gebruik te maak van propargiel alkohol as die alkohol. Dit het alkyn
funktionele polimere opgelewer. Tiol ketting end funktionele polimere was verkry deur middel van
aminolise van die polimere gesintetiseer via OAFA. Tweedens is alkohol funktionele polimere
gemodifiseer. In die geval van poli(N-vinielpirolidoon) is die OAFA grope gehidroliseer en gevolglik
is alkohole verkry op hierdie manier. Kommersiële funksionele PEG was gebruik. Die hidroksie
funksionele groep was gereageer in die Mitsunobu reaksie deur gebruik te maak van waterstof asied
(HN3) as die nukleofiel. Dit het asied funksionele ketting eindes opgelewer. Die alkyne en asied
ketting end funksionele polimere was gevolglik gebruik in die koperI gekataliseerde Huisgen 1,3-
dipolêre siklo-addisie reaksie.
Ultra Vinnige Hetero Diels-Alder kliek chemie (UVHDA) was gebruik vir die sintese van
norborneen agtige strukture (gesubstitueerde 2-tiabisiklo[2.2.1]hept-5-een groepe). Monomere was
gesintetiseer deur gebruik te maak van fenieletiel(di-etoksifosforiel)di-tioformaat en siklopentadiëen
of siklopentadiëen-getermineerde PEG. Die sintese van makromonomere is verkry via UVHDA deur
gebruik te maak van polistireen, gesintetiseer deur middel van OAFO (waar fenieletiel(dietoksifosforiel)
di-tioformaat gebruik is as OAFO agent), en siklopentadiëen of siklopentadiëengetermineerde PEG. Die makromonomere wat verkry is, is verder gebruik vir homo- en
kopolimerisasie deur middel van Ring Opening Metatesis Polimerisasie, ROMP. Vir die ROMP is vier
verskillende Grubbs tipe kataliste gebruik.
Die ring-spanning bevorderde die Huisgen 1,3,-dipolêre siklo-addissie reaksie waar siklooketyne
gebruik is as die alkyne. Die ring-spanning in die molekule laat toe vir vinninge reaksies by
kamer temperatuur. Die reaksie het die potensiaal vir interessante biologiese toepassings aangesien
dit nie ’n kopper katalis vereis nie wat toksies van aard is. In die studie word drie roetes ten einde to
siko-oktyn ondersoek. PEG was geketting end gefunksionaliseerd met die gevolgde siko-oktyne
afgeleides.
Verskillende kliek chemie metodologiëe was toegepas vir die sintese van verskillende
makromolekulêre argitekture. Resultate sluit in een nuwe tipe OAFO agent wat maklike konjugasie
met substrate bewerkstellig, ketting einde modifikasie van polimere, nuwe monomere en polimere
wat gesintetiseer is.

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/3985
Date03 1900
CreatorsAkeroyd, Niels
ContributorsKlumperman, Bert, University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science.
PublisherStellenbosch : University of Stellenbosch
Source SetsSouth African National ETD Portal
LanguageEnglish
Detected LanguageUnknown
TypeThesis
RightsUniversity of Stellenbosch

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