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Synthesis and characterisation of amphiphilic block copolymersMorkel, Charl Ernst 03 1900 (has links)
Thesis (PhD (Chemistry and Polymer Science)--University of Stellenbosch, 2005. / This study involves the synthesis and characterisation of PEG-based amphiphilic block
copolymers for the hydrophilization of polysulphone ultrafiltration membranes. PEG
based macro RAFT agents were synthesized and characterised. PEG-b-PS block
copolymers were synthesized via the RAFT assisted controlled free radical polymerisation
utilizing the synthesized PEG macro RAFT agents. The resulting polymerisation products
were then analyzed by two-dimensional chromatography at the “critical conditions” for PS.
In the second phase of this study PEG-b-PSU block copolymers were synthesized via the
polycondensation of bis (4-chlorophenyl) sulphone, Bisphenol A, and PEG. The resulting
products were characterised by NMR spectrometry.
PEG-b-PS films and modified PSU membranes (modified by the addition of PEG-b-PSU
block copolymer to the membrane casting solution) were prepared and analyzed. Surface
analyses included static contact angle, AFM force-distance analysis, and FTIR-PAS
analysis.
Results showed the successful synthesis of both PEG-b-PS and PEG-b-PSU amphiphilic
block copolymers. Surface analysis proved the successful hydrophilization of the surface
of the modified PSU membranes.
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Reversible addition fragmentation chain transfer (RAFT) mediated polymerization of N-vinylpyrrolidonePound, Gwenaelle 03 1900 (has links)
Thesis (PhD (Chemistry and Polymer Science)--University of Stellenbosch, 2008. / Xanthate-mediated polymerization was investigated as a tool for the preparation
of well-defined poly(N-vinylpyrrolidone) and copolymers of N-vinylpyrrolidone. Some
results regarding the monomer vinyl acetate are included, mostly for comparison
purposes. The structure of the leaving/reinitiating group of the xanthate mediating agent
was tuned to match the monomer reactivity. This was achieved by studying the
initialization behaviour of monomer-xanthate systems via in situ 1H-NMR spectroscopy.
Additionally, the latter technique was valuable to identify side reactions affecting the
monomer, xanthate and/or polymeric species. Subsequently, experimental conditions
were defined, and used to optimize the level of control achieved during polymerization.
Block copolymers were prepared from a xanthate end-functional poly(ethylene
glycol) with both vinyl acetate and N-vinylpyrrolidone. Finally, the preparation of
poly(N-vinylpyrrolidone) with a range of well-defined end groups was achieved via postpolymerization
treatment of the xanthate end-functional polymerization product. 3
different routes were investigated, which lead to poly(N-vinylpyrrolidone) with 1)
aldehyde or alcohol, 2) thiol or 3) unsaturated ω-chain-end functionality, in high yield,
while the α-chain-end functionality is defined by the structure of the xanthate leaving
group. The ω-aldehyde end-functional poly(N-vinylpyrrolidone) was successfully
conjugated to the lysine residues of the model protein lysozyme via reductive amination.
Particular attention was drawn to characterizing the polymerization products.
NMR spectroscopy, liquid chromatographic and mass-spectroscopic techniques were
used. The major achievements emerging from polymer analysis carried out in this study
included the following:
- a library of NMR chemical shifts for N-vinylpyrrolidone derivatives;
- an estimation of the critical conditions for poly(N-vinylpyrrolidone) relevant for
separation according to the polymer chain-ends;
- conditions for the separation of block-copolymers comprising a poly(ethylene
glycol) segment and a poly(N-vinylpyrrolidone) or poly(vinyl acetate) segment
via liquid chromatography; - valuable results on matrix-assisted laser ionization-desorption time-of-flight mass
spectroscopy (MALDI-ToF-MS) of poly(N-vinylpyrrolidone).
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Novel siloxane block copolymersStaisch, Ingrid 12 1900 (has links)
Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The research presented in this dissertation was concerned with the living radical
polymerization (LRP) of an amphiphilic, water-soluble, bi-substituted and
biologically compatible acrylamide derivative, namely n-acryloylmorpholine (NAM).
The primary objective of this research was the synthesis of novel block
copolymers containing poly(dimethylsiloxane) (PDMS) and various chain lengths
of poly(acryloylmorpholine) (polyNAM) using a LRP technique, namely reversibleaddition
fragmentation chain transfer (RAFT) polymerization. This is the first report
on the synthesis of these block copolymers using RAFT polymerization. These
novel siloxane block copolymers were synthesized using a monohydroxyterminated
PDMS material which had to first be modified into a thiocarbonylthiocontaining
moiety in order for it to be used as macromolecular chain transfer agent
(macroCTA) in the RAFT copolymerization with NAM.
Suitable reaction conditions for the synthesis of these novel block copolymers had
to, firstly, be determined, and secondly, optimized. In order to determine suitable
reaction conditions, a series of homopolymerizations with NAM were first
performed in order to compare which chain transfer agent (CTA), solvent,
temperature etc. could possibly be best suited for the block copolymerizations of
PDMS-b-polyNAM. Reported in this work is the first account of the
homopolymerization of NAM and 2-(dodecylsulfanyl)thiocarbonylsulfanyl-2-methyl
propionic acid (DMP) as CTA using RAFT polymerization.
The resulting novel siloxane block copolymers are amphiphilic in nature and the
existence of these structures was confirmed by size exclusion
chromatography/multiangle light scattering (SEC/MALS), proton nuclear magnetic
resonance (1H-NMR) spectroscopy, gel elution chromatography (GEC) and
transmission electron microscopy (TEM). Interesting phase behaviour was
observed in the latter technique.
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Chemical modification of polysaccharides with hydrophilic polymers for CaCO3 crystal growth modification and filler retention, for paper applicationsMatahwa, Howard 12 1900 (has links)
Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / Polysaccharides were modified with selected polymers via the grafting technique. Both
anionic and cationic polysaccharides were prepared. Random and crosslinked graft
copolymers were also prepared. The percentage grafting was determined by gravimetric
analysis and results were confirmed by cross-polarization magic angle spinning carbon-13
nuclear magnetic resonance microscopy (CP/MAS 13C NMR). These modified biodegradable
polymers were then used to flocculate precipitated calcium carbonate (PCC). The effects of
pH, percentage grafting, crosslinker concentration and polysaccharide concentration on PCC
flocculation were evaluated. Furthermore, the effects of anionic and cationic starch, either
added to PCC sequentially or simultaneously, on PCC flocculation were also investigated.
Generally, anionically modified starch showed excellent flocculation properties, which are
desirable for the end application of PCC retention.
The effect of polyacrylic acid (PAA) and polyacrylamide (PAM) modified cellulose fibers on
calcium carbonate crystal nucleation and growth modification was investigated. When the
heterogeneous crystallization of CaCO3 was carried out in the presence of modified cellulose
fibers the CaCO3 crystals were found to be residing on the surface of the fibers. The
morphologies of the crystallized CaCO3, polymorph and fiber surface coverage were different
for cellulose materials grafted with polymers of different functionalities, meaning that there is
interaction between the crystal growth modifier and the growing nuclei.
The effect of the modified starch on the crystallization of calcium carbonate gave useful
insight into designing CaCO3 filler morphologies. It was found that the filler size,
morphology and surface properties of fillers can be tailor-made by choosing suitable CaCO3
crystallization conditions as well as a suitable crystal growth modifier. The crystallized
CaCO3 had a negatively charged surface. Results of fluorescence studies showed that the
PAA modified starch (polymeric additive used) resided on the surface of the crystals. Thus
the presence of the polysaccharide on the surface of a filler could be advantageous for
strengthening fiber–filler bonding in paper applications.
Anionic starch materials were also used to prepare anionic-starch-coated starch particles. Both
the anionic starch and anionic-starch-coated starch particles were evaluated for PCC retention
and other properties of hand sheets. When anionic-starch-coated starch particles were used
there was generally an improvement in the PCC retention, while the other paper properties
remained desirable. The success achieved with the use of anionic-starch-coated starch
particles now opens the way for the further preparation and testing of various modified starch
particles, for optimization of filler retention.
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Tailored glycopolymersRamiah, Vernon 12 1900 (has links)
Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The synthesis of glycopolymers with various comonomers as prepared via the RAFT process is
investigated.
The macro-RAFT agent poly(3-O-methacryloyl-1,2:5,6-di-O-isopropylidene-D-glucofuranose)
(PMAlpGlc) was prepared by polymerization of the glycomonomer with cumyl phenyl dithioacetate
as the chain transfer agent. Chain extension with styrene or methyl acrylate or acrylic acid afforded
novel diblock copolymers, (PMAlGlc-b-poly[styrene] or PMAGlc-b-poly[methyl acrylate] or
PMAlGlc-b-poly[acrylic acid]), with predetermined molecular weights and narrow molecular weight
distributions.
The poly(acrylic acid) based glycopolymer was used to modify the surface of CaCO3, forming
what will be referred to as a ‘sugar-coated CaCO3’ particle. This surface modifying effect was
evaluated in depth; a schematic study of the effect of reaction temperature, pH, reaction time and
glycopolymer concentration on CaCO3 crystallization was carried out. The analytical techniques
Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) were used to verify
that these ‘sugar-coated CaCO3’ particles have an increased adherence to cellulose compared to ‘non
sugar-coated’ particles.
A series of polymer configurations comprising various ratios of glycomoiety to poly(acrylic acid)
was prepared. The effect of this polymer series on CaCO3 crystallization was evaluated and the ideal
polymer configuration and its optimum synthesis conditions (i.e. reaction pH, temperature, time and
polymer concentration) that gave maximum adherence of the ‘sugar-coated CaCO3’ particle onto
cellulose were identified.
The ability of these poly(acrylic acid) based glycopolymers to increase the interaction between
CaCO3 and cellulose was then evaluated. This was done by simply mixing all three substrates, i.e.
glycopolymer, cellulose and CaCO3 together. Analysis by TGA, SEM and Thin Layer
Chromatography (TLC) revealed both the ideal polymer configuration that favoured increased adherence of the CaCO3 to cellulose and the optimum reaction conditions required for application and
testing.
In addition to studying the interaction between cellulose and CaCO3, the amphiphilic nature of
the glycopolymers was determined. Transmission Electron Microscopy (TEM) confirmed that coreshell
particles were prepared and that these particles are solvent exchangeable (in the case of styrene
and methyl acrylate glyco-blocks) or pH exchangeable (in the case of acrylic acid glyco-blocks).
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Novel electrospun fibres of amphiphilic organic-inorganic graft copolymers of poly(acrylonitrile)-graftpoly( dimethylsiloxane) for silicone composite reinforcementBayley, Gareth Michael 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Novel silicone nanocomposites were prepared using poly(acrylonitrile) (PAN) based reinforcing
fibres as well as multi-walled carbon nanotubes (MWCNTs). Compatibility of the fibre fillers with
the silicone matrix required the synthesis of novel amphiphilic, organic–inorganic graft
copolymers of PAN and poly(dimethylsiloxane) (PAN-g-PDMS). These fibre precursor materials
were synthesised via the “grafting through” technique using conventional free radical
copolymerisation. The PDMS macromonomer content in the feed was varied from 5 wt% to 25
wt% and the molecular weights of the macromonomer were 1000 g.mol-1 and 5000 g.mol-1. The
solvent medium of the precipitation reaction was optimised at a volume ratio of 98% benzene to
2% dimethylformamide (DMF). Successful incorporation of PDMS yielded graft copolymer blend
materials of PAN-g-PDMS, blended with PAN homopolymer and unreacted PDMS
macromonomer. A gradient elution profile was developed to track the successful removal of the
PDMS macromonomer via hexane extraction. The gradient profile showed that as the PDMS
content in the feed increased, the number of graft molecules in the blend increased relative to
the number of PAN homopolymer molecules. The crystallisability of the PAN segments was
shown to decrease as the PDMS content increased. The synthesised polymer was used as
precursor material for the electrospinning of fibre fillers. The electrospinning of the precursor
material was successfully achieved using 100% DMF as electrospinning solution medium. The
amphiphilic nature of the precursor material in DMF resulted in self-assembled aggregate
structures in the electrospinning solution. An increasing PDMS content was shown to affect the
aggregation of the precursor material, and resulted in an increase in the solution viscosity. The
“gel-like” solutions limited the achievable fibre morphological control when altering conventional
electrospinning parameters such as voltage, tip-to-collector distance, and solution
concentrations. The rapid evaporation and stretching of the solution during electrospinning,
combined with the phase segregated amphiphilic molecules in solution and the crystallisation of
the PAN segments resulted in (non-equilibrium morphology) fully porous fibres. The crystallinity
was shown to decrease after electrospinning of the fibre precursor materials. Successful
incorporation of surface oxidised MWCNTs into the electrospun fibres was achieved. The
content of nanotubes was varied from 2 wt% to 32 wt%. The MWCNTs reduced the mean fibre
diameters by acting as cross-linkers between the PAN segments and increasing the solution
conductivity. The nanotubes dispersed well throughout the porous structure of the fibres and
aligned in the direction of the fibre axis. Fabrication of silicone composites containing nonwoven
and aligned fibre mats (with 8 wt% MWCNTs in the fibres, and without) was successfully achieved. The compatibilisation of the PDMS surface segregated domains allowed excellent
dispersion and interaction of the PAN based fibre fillers with the silicone matrix. Mechanical
analysis showed improved properties as the PDMS content in the fibre increased. The highest
PDMS content fibres did, however, exhibit decreased properties. This was ascribed to increased
PDMS (soft and weak) content, decreased crystallinity and increased fibre diameter (lower
interfacial area). Dramatic improvements in strength, stiffness, strain and toughness were
achieved. The most significant result was an increase in strain of 470%. The mechanical results
correlated with results of SEM analysis of the fracture surfaces. The dramatic improvements in
properties were a result of the fibre strength and ductility, as well as the mechanism of
composite failure. / AFRIKAANSE OPSOMMING: Nuwe silikonnanosamestellings is berei deur gebruik te maak van poli(akrilonitriel) (PAN)
gebaseerde versterkende vesels wat multi-ommuurde koolstof nanobuisies bevat het.
Versoenbaarheid van die vesels met die silikonmatriks het die sintese van nuwe amfifiliese,
organies–anorganiese ent-kopolimere van PAN en poli(dimetielsiloksaan) (PAN-g-PDMS)
benodig. Die vesel voorlopermateriaal is deur middel van ‘n “ent-deur” vryeradikaalkopolimerisasie
gesintetiseer. Die inhoud van die PDMS makromonomeer in die reaksie het
gewissel vanaf 5% tot 25%. Die gebruik van twee verskillende molekulêre massas
makromonomere is bestudeer (1000 en 5000 g.mol-1). Die optimale oplosmiddelmengsel vir die
neerslagreaksie was 'n volume verhouding van 98% benseen tot 2% dimetielformamied (DMF).
Suksesvolle insluiting van PDMS het versnitmateriale van PAN-g-PDMS kopolimere gemeng
met PAN homopolimere en ongereageerde PDMS makromonomere gelewer. 'n Gradiënteluering-
chromatografiese profiel is ontwikkel om die suksesvolle verwydering van die PDMS
makromonomere via heksaanekstraksie te bepaal. Die gradiëntprofiel het aangetoon dat indien
die PDMS inhoud in die reagense verhoog is, die aantal entmolekules relatief tot PAN
homopolimeermolekules ook verhoog het. 'n Toename in PDMS inhoud het egter 'n afname in
kristallisasie van die PAN segmente tot gevolg gehad. Die gesintetiseerde polimeer is gebruik
as die beginmateriaal vir die elektrospin van veselvullers. Die elektrospin van die beginmateriaal
was suksesvol wanneer 100% DMF as elektrospinoplosmiddel gebruik is. Die amfifiliese aard
van die beginmateriaal in DMF lei tot outokonstruksie van aggregaatstrukture in die
elektrospinoplossing. Toenemende PDMS inhoud beïnvloed die outokonstruksie van die
molekules in oplossing en het gelei tot 'n toename in die oplossings se viskositeit. Die "gelagtige"
oplossings beperk die haalbare vesel se morfologiese beheerbaarheid wanneer
konvensionele elektrospin parameters soos elektriese spanning, punt-tot-versamelaar afstand,
en oplossingkonsentrasies gewysig word. Die vinnige verdamping en strek van die oplossing
tydens elektrospin, gekombineer met die fase-geskeide amfifiliese molekules in oplossing en die
kristallisasie van die PAN segmente, het gelei tot (nie-ewewig morfologie) volledige poreuse
vesels. Die kristalliniteit van die veselbeginmaterial het afgeneem nadat elektrospin toegepas is.
Die insluiting van die oppervlak-geoksideerde multi-ommuurde koolstof nanobuisies in die
elektrogespinde vesels was suksesvol. Die inhoud van die nanobuisies het gewissel van 2 wt%
tot 32 wt%. Die MWCNTs het die gemiddelde veseldeursnit verminder deur op te tree as
kruisbinders tussen die PAN segmente van die molekules. Die nanobuisies was goed versprei
deur die poreuse struktuur van die vesels en dit was gerig in die rigting van die vesel-as. Bereiding van die silikonsamestellings bestaande uit nie-geweefde en gerigte veseloppervlakke
(met en sonder 8 wt% multi-ommuurde koolstof nanobuisies in die vesel) was suksesvol. Die
versoenbaarheid tussen die oppervlak van die PDMS-geskeide gebiede en die silikonmatriks
laat uitstekende verspreiding en interaksie van die PAN-gebaseerde veselvullers met die
silikonmatriks toe. Meganiese analise het aangetoon dat die fisiese eienskappe verbeter het
namate die PDMS inhoud in die vesel vermeerder het. Die vesels met die hoogste PDMS
inhoud het egter verswakte eienskappe getoon. Dit is toegeskryf aan ‘n verhoogde PDMS
inhoud (sag en swak), ‘n afname in kristalliniteit en ‘n verhoogde veseldeursnit (laer
grensoppervlakke). Dramatiese verbeterings in sterkte, styfheid, verlengbaarheid, vervorming
en taaiheid is bereik. Die mees betekenisvolle gevolg was 'n toename in die verrekking van
470%. Die meganiese resultate is gekorreleer met SEM ontleding van die brekingsoppervlakke.
Die veselkrag en vervormbaarheid, sowel as die meganisme van die splyting van die
samestellings, het tot die dramatiese verbeterings in die meganiese eienskappe gelei.
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Electrospun antimicrobial and antibiofouling nanofibresGule, Nonjabulo Prudence 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The main objective of this study was to develop electrospun nanofibres with both antimicrobial and antibiofouling properties for possible application in water filtration. To do this, two routes were investigated: firstly, the use of biocides and bactericidal copper salts to introduce bactericidal properties on electrospun nanofibres. Secondly, the modification of polymers using furanone compounds to obtain nanofibres with the ability to repel microbial attachment.
Fabrication of biocide-containing PVA nanofibres was successful. This was achieved through direct doping of PVA solutions with AquaQure which is an aqueous biocide comprising of mainly Cu2+ and Zn2+, prior to the electrospinning process coupled with chemical crosslinking using glyoxal. The conventional needle based electrospinning technique was used to fabricate these nanofibrous mats. The presence of the constituents of AquaQure on surfaces of PVA/AquaQure nanofibrous mats was confirmed using energy dispersive x-ray analysis (EDX). ATR/FTIR, XRD, TGA, DSC and SEM techniques were used to do chemical and thermal analysis of the nanofibres in comparison with pristine PVA nanofibres. These nanofibres demonstrated antimicrobial activity of up to 5 log against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Because of crosslinking, these fibres also demonstrated good water stability. Leaching of the ions constituting AquaQure was limited and compared with South African national standards for drinking water, the water filtered through these nanofibress was deemed safe for human consumption. Bioluminescence imaging and fluorescence microscopy were used to confirm antimicrobial activity results obtained from plate counting. These nanofibres demonstrated satisfactory antimicrobial efficiency but did not repel microbial attachment.
The second part of this study entailed the investigation of copper-doped PVA and SMA nanofibres for antimicrobial activity. Although bactericidal properties of copper are well documented, its selection was based on the fact that it is the main constituent of the AquaQure. Bubble electrospinning was used instead of needle electrospinning to upscale nanofibre production. Similar techniques as those used in PVA/AquaQure nanofibres were used to characterize the copper functionalized nanofibres. Even though these nanofibres demonstrated exceptional antimicrobial efficacy (up to 5 log) for all the strains, bioluminescence imaging indicated a trend for these cells to enter a dormant state on contact with the copper containing-nanofibres.
The last part of this project involved testing of free furanone compounds as well as surface-tethered furanone-modified nanofibres for their antibiofouling potentials. To do this, blends of 2,5-dimethyl-4-hydroxy-3(2H)furanone (DMHF) (5% wt/vol) with PVA (10% wt/vol) were prepared and electrospun to produce PVA/DMHF nanofibres. The free furanones and furanone-modified nanofibres demonstrated not only antibiofouling properties but also antimicrobial activity. Other furanone compounds with 3(2H) and 2(5H) cores were synthesized. The synthesis of these furanone compounds (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone and 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was successful. Their structures and molar masses were confirmed using 1H NMR and ES mass spectroscopy. These furanones were then covalently immobilized on the SMA backbone. To test their antimicrobial and antibiofouling activity, the furanone-modified polymer was dissolved in an ethanol and methanol mixture (1:1) and electrospun to produce nanofibres. The free furanone and furanone-modified SMA nanofibres derived from 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone demonstrated high antibiofouling and antimicrobial efficiency against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. The 2(5H) furanone on the other hand had limited activity against the strains. These nanofibres were also characterized and compared with their pristine polymer counterparts and leaching experiments were conducted using GC-MS. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie studie was om nanovesel filtrasie nanofibre met beide antimikrobiese en aanpakwerende eienskappe te ontwikkel. Twee verskillende metodes is ondersoek. Eerstens is biosiede en bakteriee-dodende koper soute gebruik om antimikrobiese nanovesels te lewer. Tweedens is nanovesels met furanoon samestellings gemodifiseer om nanovesels te lewer wat mikrobiese aanhegting voorkom.
Die fabrisering van biosied-bevattende PVA nanovesel nanofibre was suksesvol.
AquaQure, ‟n biosied wat hoofsaaklik uit Cu2+ en Zn2+ bestaan, is direk by PVA oplossings gevoeg voor die elektrospin proses, en is gevolg deur chemiese kruisbinding deur middel van “glyoxal”. Die nanovesels is neergele in ‟n ongeweefde mat deur middel van die konvensionele naald-gebasseerde elektrospin proses. Verspreidings X-staal analises (EDX) is gebruik om die teenwoordigheid van AquaQure komponente in en op die oppervlakte van die PVA/aquaqure nanovesel matte te bevestig. ATR/FTIR, UV-Vis, XRD, TGA, DSC en SEM tegnieke is gebruik vir chemiese en termiese analises om sodoende PVA/aquacure nanovesels met ongemodifiseerde PVA nanovesels te vergelyk. PVA/aquacure nanovesels het ‟n antimikrobiese aktiwiteit van tot 5 log reduksie getoon teen Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 en K. pneumoniae Xen 39. Die vesels was stabiel in water na kruisbinding. Slegs beperkte uitloging van Aquaqure Cu2+ en Zn2+ ione is waargeneem, en water wat deur die PVA/aquacure nanovesels gefiltreer is, is volgens Suid Afrikaanse Nasionale Standaarde vir drinkwater steeds veilig vir menslike gebruik. Behalwe vir die plaat-tellingsmetode het bio-lumiserende fotos en fluoroserende mikroskopie ook die antimikrobiese aktiwiteit van die vesels bevestig. Die vesels het bevredigende antimikrobiese efektiwiteit getoon, maar kon nie mikrobiese aanhegting voorkom nie.
In die tweede gedeelte van die werk is die antimikrobiese aktiwiteit van PVA en SMA vesels wat met koper verreik is, ondersoek. Alhoewel die bakteriee dodende eienskappe van koper reeds goed gedokumenteer is, is hierdie ondersoek gedoen op grond van die feit dat koper een van die hoof komponente van aquaqure is. Nanovesels is uit koper-verreikte oplossings van PVA en SMA deur middel van die borrel-gebasseerde elektrospin tegniek gefabriseer, ten einde die opbrengs van nanovesels te verhoog. Fisiese kruisbinding deur middel van hitte behandeling is toegepas ten einde die stabiliteit van die vesels in water te verbeter. Dieselfde karakteriseringstegnieke wat gebruik is vir die PVA/aquacure vesels is op hierdie vesels toegepas. Alhoewel die vesels uitstekende antimikrobiese aktiwiteit van tot 5 log reduksie gedemonstreer het, het bio-lumiserende beeldvorming getoon dat die selle ‟n dormante stadium binnegaan na kontak met hierdie vesels. In die laaste gedeelte van die projek is vrye furanoon samestellings en nanofibre met oppervlak-gehegde furanone getoets vir aanpakwerende potensiaal. Om dit te bewerkstellig was „n mengsel van 2,5 – dimethyl-4-hydroxy-3(2H) furanone (DMHF) (5% wt/vol) en PVA (10% wt/vol) voorberei en gebruik om PVA/DMHF nanovesel filtrasie nanofibre te produseer deur middel van die elektrospin proses. Die vrye furanone en furanoon-gemodifiseerde nanofibre het nie alleen aanpak weerstandbiedende einskappe gedemonstreer nie maar ook antimikrobiese eienskappe. DMHF was gebruik as die begin material om furanoon samestellings te produseer met 3(2H) en 2(5H) kerne. Die sintesis van hierdie furanone se samestellings (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone en 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was suksesvol. Hulle strukture en molere massas was bevestig met 1H NMR en ES massa spektrometrie. Hierdie furanone is daarna kovalent ge-immobiliseer op die SMA rugbeen. Om hulle antimikrobiese en aanpakwerende aktiwitiet te toets, is die furanoon-gemodifiseerde polimeer opgelos in „n etanol en metanol mengsel (1:1) en ge-elektrospin om nanovesel filtrasie nanofibre te produseer. Die furanone en furanoon-gemodifiseerde nanovesel filtrasie nanofibre afkomstig van 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone het hoe aanpakwerende en antimibrobiese effektiewitiet getoon teenoor die Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Hierdie nanovesel filstrasie nanofibre is ook gekarakteriseer en vergelyk met die ongemodifiseerde polimeer. „n Uitlogings eksperiment is uitgevoer deur gebruik te maak van GC-MS.
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Synthesis, properties and analysis of polydadmac for water purificationJohn, Wilson 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: This study concerns the synthesis, properties and quantitative analysis of polydiallyldimethylammonium chloride (polyDADMAC), a water-soluble polymer used world-wide for potable water purification. The special interest in this polymer is the result of its widespread use and the current lack of adequate analytical methods for it. This is especially important for water treatment organisations.
A novel gel permeation chromatography (GPC) method was developed and evaluated for polymer analysis. The scope was extended to determine the presence of unreacted monomer (DADMAC) as well as the percentage active polymer.
polyDADMAC was first prepared using a known synthesis method. The product was purified and characterized by GPC and 13C-NMR spectroscopy. New and conclusive evidence of the existence of a five-member pyrrolidine ring system was obtained. A proposed mechanism of polymerization was determined. The activity of the synthesized polyDADMAC was evaluated and it was found to perform effectively as a coagulant.
The physical and chemical properties of polyDADMAC were then studied under simulated water treatment conditions. The polymer reaction with chlorine revealed the formation of trihalogenated methane compounds (THMs). Gas chromatography–mass spectrometry (GC–MS) was used to conclusively identify the formation of chloroform.
The polymer stability under different conditions of heat exposure, UV radiation and pH variations was studied. GPC results indicated that polyDADMAC is a very stable polymer and undergoes structural change only when subjected to extremes of pH, temperature and UV conditions. Results of a short study on microbial degradation indicated growth of the cultures, and subsequent polymer degradation. Reactions of polyDADMAC were concluded with a study of the impact of ozone on polyDADMAC. GPC results indicated a significant change in the ozonated polymer peak profile.
Analytical methods to determine polyDADMAC residues in water were reviewed and critically evaluated. Methods based on complex formation/spectroscopy suffered from severe limitations and produced no meaningful results, contrary to claims made by previous researchers. Colloid titration based on an established method was promising but required extensive modification for quantitative analysis. Finally four novel methods were developed, including: solid phase extraction, membrane filtration-GPC, the HACH complexation method, and a GPC method with indirect UV detection.
The study is concluded with a chemical risk assessment that indicated minimal human health risks associated with the production and use of polyDADMAC. / AFRIKAANSE OPSOMMING:Hierdie studie behels die sintese, eienskappe en kwantitatiewe analise van polidiallielmetielammoniumchloried (polyDADMAC), 'n wateroplosbare polimeer wat wêreldwyd vir drinkwatersuiwering gebruik word. Die belangstelling in hierdie spesifieke polimeer is as gevolg van die wydverspreide gebruik daarvan en die feit dat daar tans onvoldoende eenvoudige analitiese metodes daarvoor bestaan. Dit is veral belangrik vir waterbehandelingsorganisasies.
'n Nuwe gelpermeasiechromatografie (GPC) metode is ontwikkel en geevalueer vir die analise van hierdie polimeer. Die omvang van die studie is later uitgebrei om die teenwoordigheid van ongereageerde monomeer (DADMAC) asook die persentasie aktiewe polimeer te bepaal.
polyDADMAC is eers volgens 'n bekende sintesemetode berei. Die produk is gesuiwer en gekarakteriseer m.b.v. GPC en 13C-KMR. Nuwe bewyse vir die bestaan van 'n vyflid pirollidoonringsisteem is verkry. 'n Meganisme vir hierdie polimerisasie metode is vasgestel. Die aktiwiteit van die bereide polyDADMAC is geevalueer en daar is bevind dat dit effektief as koaguleermiddel optree.
Daarna is die chemiese en fisiese eienskappe van polyDADMAC onder gesimuleerde waterbehandelingskondisies bepaal. polyDADMAC het met chloor gerageer om trihalogeneerde metaanverbindings (THMs) te vorm. Gaschromatografie–massa-spektrometrie (GC–MS) is gebruik om die ontstaan van chloroform te bevestig.
Daarna is die stabiliteit van die polimeer onder verskei reaksiekondisies bepaal: hitte, UV-bestraling, en pH. GPC-resultate het aangeduiui dat polyDADMAC baie stabiel is en ondergaan strukturele veranderings slegs onder uiterste kondisies van pH, temperatuur en UV. 'n Kort studie van die effek van mikro-organismes op polyDADMAC het egtermikrobiese kultuurgroei met die gevolglike afbreek van die polimeer getoon. Resultate van 'n studie van die impak van osoon op polyDADMAC het getoon dat daar 'n groot verandering in die GPC-profiel van die ge-osoneerde vorm van die polimeer was.
Verdere analitiese metodes wat al gebruik is om polyDADMAC residue in water te bepaal, is uitgevoer en krities geevalueer. Metodes gebasseer op kompleksvorming/ spektroskopie het erge beperkings gehad en het nie betekenisvolle resultate gelewer nie. Dit was in teenstelling met wat voorheen deur ander navorsers bevind is. 'n Kolloiedtitrasie gebasseer op 'n bestaande metode het goeie resultate gelewer maar het omvattende veranderings benodig om kwantitatiewe resultate te lewer. Ten slotte is vier nuwe metodes ontwikkel: soliede fase-ekstraksie, membraanfiltrasie-GPC, die HACH-komplekseringsmetode, en 'n GPC-metode met indirekte UV-waarneming..
Die studie is afgesluit met 'n bepaling van die chemiese risiko wat poly DADMAC vir die gesondheid van die mens inhou. Daar is tot die gevolgtrekking gekom dat die produksie en gebruik van poly DADMAC slegs‘n minimum gesondheidsrisiko inhou.
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The use of chromium/bis(diphenylphosphino)amine catalysts in tandem ethylene copolymerization processesDu Toit, Aletta 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The possibility of utilizing the chromium/bis(diphenylphosphino)amine (PNP) type of
catalysts in ethylene polymerization processes was investigated. These processes
include the production of linear low density polyethylene (LLDPE), the production of
polyethylene waxes and the synthesis of special comonomers for ethylene
copolymerization.
The chromium/Ph2PN{CH(CH3)2}PPh2 tetramerization system was used in
combination with a polymerization catalyst to yield ethylene copolymers with
controlled branching. Copolymers with bimodal chemical composition distributions
were obtained in these tandem reactions. This chromium/PNP-type tetramerization
catalyst and metallocene polymerization catalysts are not completely compatible in
tandem catalytic systems due to different optimum temperatures for their effective
functioning. The oligomerization to polymerization catalyst ratios, the catalyst to
cocatalyst ratios and the temperature profile are all factors influencing the amount of
-olefins formed and therefore the type of copolymer produced. The activity of the
polymerization catalyst decreases in the presence of the oligomerization catalyst,
indicating that the two catalysts interfere chemically. The main difference between
copolymers produced in conventional or tandem fashion is the presence of a small
amount of low molecular weight material produced by the oligomerization catalyst
and also the presence of a highly crystalline component. The latter component
results from the initial low concentration of a-olefins in the first conversion, but such a
component is also independently produced by the oligomerization catalyst.
LLDPE with butyl branches is obtained when a selective trimerization catalyst is used
in combination with a polymerization catalyst. The chromium/(o-OMeC6H4)2
PN(CH3)P(o-OMeC6H4)2 trimerization system is more suitable than the
chromium/Ph2PN{CH(CH3)2}PPh2 tetramerization system for use in tandem reactions
with a metallocene catalyst due to its high activity and selectivity at higher
temperatures. The chemical composition distribution varies with an increase in
reaction time due to the increasing amount of 1-hexene produced. Comparison of
CRYSTAF traces of tandem copolymers with conventional copolymers show that the
tandem copolymers have a broader chemical composition distribution. Addition of 1-
hexene during the course of a conventional copolymerization reaction produces
copolymers with similar chemical composition distributions to that of the tandem copolymers. Later addition of the polymerization catalyst to the oligomerization
reaction mixture results in copolymers with higher comonomer content, similar to
conventional copolymers.
Chromium/(o-EtC6H4)2PN(CH3)P(o-EtC6H4)2 is not suitable for LLDPE production in
tandem reactions, since it is selective to higher oligomers or polyethylene waxes at
higher temperatures. Variation of the MAO cocatalyst and hydrogen concentrations
significantly influences the yield, viscosity and crystallization behaviour of the waxlike
products. Low MAO concentrations resulted in multiple melting peaks, while
higher concentrations display single melting peaks and lower viscosity values.
Ethylene co-oligomerization reactions with styrene or p-methylstyrene using the
chromium/PNP-type oligomerization technology produce various phenyl-hexene and
phenyl-octene isomers either through cotrimerization or cotetramerization. The
known ethylene trimerization catalysts show cotrimerization behaviour, while the
catalysts with known selectivity for ethylene tetramerization also yield
cotetramerization products. Chromium complexes that contain the more bulky
ligands display lower selectivity towards co-oligomerization and greater preference
for ethylene homotrimerization.
These co-oligomerization products can be incorporated into a polyethylene chain by
copolymerization in a simultaneous or sequential tandem reaction. The combined
co-oligomerization-polymerization reactions yield copolymers with lower crystallinity
than obtained from the conventional ethylene-styrene copolymerization reaction due
to higher comonomer incorporation. The polymer yields are higher in the cooligomerization-
copolymerization reactions. The ability of the different cooligomerization
products to incorporate into the polyethylene chain was established:
unreacted styrene and the more bulky isomers, 3-phenyl-1-hexene and 3-phenyl-1-
octene, are not incorporated readily, while branches resulting from 4-phenyl-1-
hexene, 4-phenyl-1-octene, 5-phenyl-1-octene and 6-phenyl-1-octene are detected in
the NMR spectrum. / AFRIKAANSE OPSOMMING: Die moontlikheid om die chroom/bis-(difenielfosfino)amien (PNP) tipe katalisatore in
etileen-polimerisasie reaksies te gebruik is ondersoek. Hierdie prosesse sluit die
produksie van lineêre lae digtheid poliëtileen (LLDPE), die produksie van
poliëtileenwasse en die sintese van spesiale komonomere vir etileenkopolimerisasie
in.
Die chroom/Ph2PN{CH(CH3)2}PPh2 tetramerisasie-sisteem is gebruik in kombinasie
met ¢n polimerisasiekatalisator om etileenkopolimere met gekontroleerde vertakkings
te vorm. Kopolimere met ‘n bimodale chemiese samestellingsverspreiding word
verkry in hierdie tandemreaksies. Hierdie chroom/PNP-tipe tetramerisasiekatalisator
en die metalloseenkatalisators is nie heeltemal verenigbaar in die tandemsisteem nie
weens verskille in hul optimum reaksietemperature vir effektiewe funksionering. Die
oligomerisasie tot polimerisasiekatalisatorverhouding, die katalisator tot
kokatalisatorverhouding en die temperatuurprofiel is almal faktore wat die gevormde
hoeveelheid -olefiene beinvloed, en dus die tipe kopolimeer wat gevorm word. Die
aktiwiteid van die polimerisasiekatalisator verminder in die teenwoordigheid van die
oligomerisasiekatalisator, wat aandui dat die twee katalisatore chemies met mekaar
inmeng. Die duidelikste verskil tussen die kopolimere wat geproduseer word op die
konvensionele of die tandem manier is die teenwoordigheid van ‘n klein hoeveelheid
lae molekulere massa materiaal wat gevorm word deur die oligomerisasiekatalisator,
asook ‘n komponent met baie hoë kristalliniteit. Die laasgenoemde komponent
ontstaan weens die aanvanklike lae konsentrasie van die a-olefiene in die eerste
omsetting, maar so ‘n komponent word ook onafhanklik gevorm deur die
oligomerisasiekatalisator.
LLDPE met butiel-vertakkings word verkry wanneer ‘n selektiewe
trimerisasiekatalisator in kombinasie met ‘n polimerisasiekatalisator gebruik word.
Die chroom/(o-OMeC6H4)2PN(CH3)P(o-OMeC6H4)2 trimerisasiesisteem is meer
geskik as die chroom/Ph2PN{CH(CH3)2}PPh2 tetramerisasiesisteem vir gebruik in
tandem met ‘n metalloseenkatalisator weens die katalisator se hoë aktiwiteit en
selektiwiteid vir 1-hekseen by hoër reaksietemperature. Die chemiese
samestellingsverspreiding verander soos die reaksietyd toeneem weens die
toenemende hoeveelheid 1-hekseen wat gevorm word. Vergelyking van die
CRYSTAF-diagram van die tandemkopolimere met konvensionele kopolimere toon dat die tandemkopolimere ‘n wyer chemiese samestellingsverspreiding het.
Geleidelike byvoeging van 1-hekseen gedurende die loop van ‘n konvensionele
reaksie, vorm kopolimere met ‘n soortgelyke chemiese samestelingsverspreiding as
die tandemkopolimere. Latere byvoeging van die polimerisasiekatalisator lei tot die
vorming van kopolimere met ‘n hoër komonomeerinhoud, soortgelyk aan die
konvensionele kopolimere.
Chroom/(o-EtPC6H4)2PN(CH3)P(o-EtC6H4)2 is nie geskik om LLDPE in
tandemreaksies te vorm nie, aangesien dit selektief is vir hoër oligomere of
poliëtileenwasse by hoër reaksietemperature. Variasie van die MAO-kokatalisator en
die waterstofkonsentrasies beinvloed die hoeveelheid produk wat gevorm word,
asook die viskositeit en kristallisasiegedrag daarvan. Lae MAO konsentrasies lei tot
meer as een smeltpiek, terwyl hoër konsentraises ‘n enkelpiek vertoon. Die
viskositeit van die produkmengsel is ook laer.
Die gebruik van die chroom/PNP-tipe oligomerisasietegnologie in etileenkooligomerisasiereaksies
met stireen, lei tot die vorming van verskeie feniel-hekseenen
fieniel-okteenisomere deur of kotrimeriasie, of kotetramerisasie. Katilisatore met
bekende etileentrimerisasieligande vertoon kotrimerisasiegedrag terwyl die ligande
wat bekend is vir selektiwiteit in etileentetramerisasie, kotetramerisasieprodukte
vorm. Die chroomkomplekse met die meer bonkige ligande het laer selektiwiteit vir
ko-oligomerisasie en vertoon ‘n groter voorkeur vir etileenhomo-trimerisasie.
Die ko-oligomerisasieprodukte kan in ‘n poliëtileenketting ingebou word deur kopolimerisasie
in ‘n gelyktydige of opeenvolgende tandemreaksie. Die
gekombineerde ko-oligomerisasie-polimerisasiereaksie vorm kopolimere van ‘n laer
kristalliniteit as wat gevind word met die konvensionele etileen-stireen
kopolimerisasie reaksie weens hoer komonomeerinkorporasie. Meer polimeer word
gevorm in die ko-oligomerisasie-kopolimerisasie reaksie. Die vermoë van die
verskillende ko-oligomerisasieprodukte om in die poliëtileenketting ingesluit te word
is bepaal. Ongereageerde stireen en die meer bonkige isomere, 3-feniel-1-hekseen
en 3-feniel-1-okteen, word nie maklik ingevoeg nie. Vertakkings as gevolg van die
inkorporasie van 4-feniel-1-hekseen, 4-feniel-1-okteen, 5-feniel-1-okteen and 6-
feniel-1-okteen kan waargeneem word in die KMR spektrum.
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Synthesis of permanent non-leaching antimicrobial polymer nanofibersBshena, Osama E. S. 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Antimicrobial fibers are very useful in various fields such as air and water purification,
wound dressings and protective bandages, where sterile environments are essential. The nonwoven
nanofiber mats or membranes are able to filter out microorganisms and potentially
kill several threatening pathogenic bacteria. In this thesis, a variety of styrene-maleimide
copolymer derivatives were prepared based on the modification of poly(styrene-co-maleic
anhydride with various primary amine compounds.
All prepared copolymer derivatives were electrospun to nanofiber mats using the needle
electrospinning technique. For the characterization, differential scanning calorimetry (DSC)
and thermogravimetric analysis (TGA) were used to study the thermal properties of the
electrospun fiber mats. Scanning electron microscopy (SEM) was carried out to observe fiber
dimensions and morphology.
The antibacterial activity of electrospun fiber mats was evaluated against different bacteria
including Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas
aeruginosa (Gram-negative). The evaluation study utilized different tools to test for
antibacterial activity and mode of cell death, including bioluminescent imaging, fluorescence
imaging and the viable cell counting method. Excellent antimicrobial activity was obtained
against the different strains especially against Staphylococcus aureus. Fiber mats containing
tertiary amino groups, phenol or quaternary ammonium groups had the strongest
antimicrobial properties. / AFRIKAANSE OPSOMMING: Antimikrobiese vesels is baie nuttig in verskeie toepassingsgebiede, soos lug- en
watersuiwering, wondbedekkings en beskermende verbande, waar ‘n steriele omgewing
noodsaaklik is. Die ongeweefde nanovesel matte of membrane is in staat om mikroorganismes
te verwyder deur filtrasie, maar kan ook verskeie patogeniese bakterieë
doodmaak. In hierdie proefskrif is ‘n verskeidenheid stireen-maleimied kopolimeer
afgeleides gesintetiseer, gebaseer op die modifikasie van poli(stireen-ko-maleïne anhidried)
met verskeie primêre amien verbindings.
Nanovesel matte van al die gesintetiseerde kopolimeer afgeleides is gemaak deur gebruik te
maak van die naald-elektrospin tegniek. Die termiese eienskappe van hierdie nanovesel matte
is bestudeer deur gebruik te maak van differensiële skandeer kalorimetrie (DSK) en
termogravitasie analiese (TGA) as karakteriseringsmetodes. Die vesel dimensies en
morfologie is bestudeer deur skandeer elektronmikroskopie as karakteriseringsmetode te
gebruik.
Die antibakteriële aktiwiteit van die gespinde vesel matte is geëvalueer teen verskillende
bakterieë, naamlik Staphylococcus aureus (Gram-positief), Escherichia coli en Pseudomonas
aeruginosa (Gram-negatief). Die evalueringstudie het verskillende instrumente gebruik om
vir antibakteriële aktiwiteit en meganisme van seldood te toets, insluitend bioluminiserings
beelding, fluoressensie beelding en die lewensvatbare sel tellingsmetode. Uitstekende
antimikrobiese aktiwiteit is verkry teen die verskillende rasse, veral teen Staphylococcus
aureus. Vesel matte met tersiêre aminogroepe, fenol of kwaternêre ammoniumgroepe het die
sterkste antimikrobiese eienskappe gehad.
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