Thesis (DSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Examples
of
the
use
of
NMR
spectroscopy
in
the
study
of
radical
polymerization
processes
have
been
described.
The
studies
presented
have
made
a
significant
contribution
to
the
understanding
of
the
fundamental
mechanistic
processes
in
these
polymerization
systems.
It
is
pointed
out
that
NMR
in
conventional
radical
polymerization
is
of
limited
use
due
to
the
concurrent
occurrence
of
all
elementary
reactions
(initiation,
propagation
and
termination).
Conversely,
for
living
radical
polymerization,
NMR
has
great
value.
In
that
case,
the
elementary
reactions
are
somewhat
more
restricted
to
specific
times
of
the
polymerization
process.
This
allows
for
example
the
detailed
study
of
the
early
stages
of
chain
growth
in
Reversible
Addition-‐Fragmentation
Chain
Transfer
(RAFT)
mediated
polymerization.
Two
different
studies
are
described.
The
first
is
related
to
the
early
stages
of
RAFT-‐mediated
polymerization.
A
process
for
which
we
coined
the
name
initialization
was
studied
via
in
situ
1H
NMR
spectroscopy.
It
is
shown
that
in
many
cases,
there
is
a
selective
reaction
that
converts
the
original
RAFT
agent
into
its
single
monomer
adduct.
A
few
different
examples
and
their
mechanistic
interpretation
are
discussed.
It
is
also
shown
that
NMR
spectroscopy
can
be
a
valuable
tool
for
the
assessment
of
a
RAFT
agent
in
conjunction
with
a
specific
monomer
and
polymerization
conditions.
In
the
second
study,
15N
NMR,
31P
NMR
and
1H
NMR
are
used
for
two
different
types
of
experiments.
The
first
is
a
conventional
radical
copolymerization
in
which
the
growing
chains
are
trapped
by
a
15N
labeled
nitroxide
to
yield
a
stable
product.
In
the
second
experiment,
a
similar
copolymerization
is
conducted
under
nitroxide-‐mediated
conditions.
The
nitroxide
of
choice
contains
phosphorous,
which
enables
the
quantification
of
the
terminal
monomer
in
the
dormant
chains.
Each
of
the
experiments
individually
provides
interesting
information
on
conventional
radical
copolymerization
and
nitroxide-‐mediated
copolymerization,
respectively.
Combination
of
the
experimental
data
reveals
an
interesting
discrepancy
in
the
ratio
of
terminal
monomer
units
in
active
chains
and
dormant
chains.
Although
not
unexpected,
this
result
is
interesting
and
useful
from
a
mechanistic
as
well
as
a
synthetic
point
of
view.
In
terms
of
future
perspectives,
it
is
expected
that
the
advanced
analytical
techniques
as
described
here
will
remain
crucial
in
polymer
science.
Present
developments
in
radical
polymerization,
such
as
investigations
into
monomer
sequence
control,
rely
on
accurate
knowledge
of
kinetic
and
mechanistic
details
of
elementary
reactions.
It
is
expected
that
such
detailed
studies
will
be
a
main
challenge
for
the
next
decade
of
polymer
research. / AFRIKAANSE OPSOMMING: Voorbeelde
van
die
gebruik
van
KMR-‐spektroskopie
in
die
studie
van
radikaalpolimerisasies
word
beskryf.
Hierdie
studies
het
ʼn
beduidende
bydrae
gelewer
tot
die
verstaan
van
die
fundamentele
meganistiese
prosesse
in
hierdie
polimerisasiesisteme.
Dit
het
daarop
gewys
dat
KMR
beperkte
gebruike
het
in
konvensionele
radikaalpolimerisasies
as
gevolg
van
die
gelyktydige
voorkoms
van
alle
basiese
reaksies
(afsetting,
voortsetting
en
beëindiging).
Aan
die
anderkant
het
KMR
groot
waarde
vir
lewende
radikaalpolimerisasie.
In
hierdie
geval
is
die
elementêre
reaksies
ietwat
meer
beperk
tot
spesifieke
tye
van
die
polimerisasieproses.
Gedetailleerde
studies
kan
byvoorbeeld
van
die
vroeë
stadiums
van
die
kettinggroei
in
Omkeerbare
Addisie-‐Fragmentasie-‐
KettingOordrag
(OAFO)-‐bemiddelde
polimerisasie
gedoen
word.
Twee
verskillende
studies
is
beskryf.
Die
eerste
het
betrekking
op
die
vroeë
stadiums
van
die
OAFO-‐bemiddelde
polimerisasie.
'n
Proses
wat
“inisialisering”
genoem
is,
is
bestudeer
deur
middel
van
in
situ
1H
KMR-‐spektroskopie.
Dit
is
bewys
dat
daar
in
baie
gevalle
'n
selektiewe
reaksie
is
wat
die
oorspronklike
OAFO-‐agent
in
sy
enkelmonomeeradduk
verander
voor
polimerisasie.
'n
Paar
ander
voorbeelde
en
hul
meganistiese
interpretasie
is
bespreek.
Dit
is
ook
bewys
dat
KMR-‐spektroskopie
'n
waardevolle
hulpmiddel
kan
wees
vir
die
assessering
van
'n
OAFO-‐agent
in
samewerking
met
'n
spesifieke
monomeer
en
polimerisasie
toestande.
In
die
tweede
studie
is
15N
KMR,
31P
KMR
en
1H
KMR
gebruik
vir
twee
verskillende
tipes
van
die
eksperiment.
Die
eerste
is
'n
konvensionele
radikaalkopolimerisasie
waarin
die
groeiende
kettings
vasgevang
word
deur
'n
15N-‐gemerkte
nitroksied
om
'n
stabiele
produk
te
lewer.
In
die
tweede
eksperiment
is
'n
soortgelyke
kopolimerisasie
gedoen
onder
nitroksied-‐
bemiddelde
toestande.
Die
gekose
nitroksied
bevat
fosfor
wat
die
kwantifisering
van
die
terminale
monomeer
in
die
dormante
kettings
moontlik
maak.
Elkeen
van
die
individuele
eksperimente
lewer
interessante
inligting
oor
konvensionele
radikale
kopolimerisasie
en
nitroksied-‐bemiddelde
kopolimerisasie,
onderskeidelik.
ʼn
Kombinasie
van
die
eksperimentele
data
toon
'n
interessante
verskil
aan
in
die
verhouding
van
die
terminale
monomeereenhede
in
die
aktiewe
en
sluimerende
kettings.
Alhoewel
dit
nie
onverwags
is
nie,
is
die
resultate
interessant
en
van
waarde
vanuit
'n
meganistiese-‐
sowel
as
'n
sintetiese
oogpunt.
In
terme
van
toekomstige
perspektiewe
word
daar
verwag
dat
gevorderde
analitiese
tegnieke
soos
hier
beskryf,
belangrik
sal
bly
in
polimeerwetenskap.
Huidige
ontwikkelinge
in
radikaalpolimerisasie,
soos
ondersoeke
na
die
beheer
van
monomeervolgorde,
maak
staat
op
akkurate
kennis
van
kinetiese
en
meganistiese
besonderhede
van
die
basiese
reaksies.
Daar
word
verwag
dat
sulke
gedetailleerde
studies
ʼn
uitdaging
sal
bied
vir
die
volgende
dekade
van
polimeernavorsing.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71596 |
| Date | 12 1900 |
| Creators | Klumperman, Bert |
| Contributors | Mallon, Peter 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 | English |
| Type | Thesis |
| Format | iv, 87 p. : ill. |
| Rights | Stellenbosch University |
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