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Dissertation (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Polymers prepared via radical techniques are very common in our every day environment. The technique is however limited by a lack of control over the polymerization and an inability to produce block copolymers. Block copolymers have a significant number of potential applications in advanced materials and as a result are a field in which significant research is being conducted. Reversible Addition-Fragmentation chain transfer (RAFT) is a living free radical process that overcomes the disadvantages inherent in the traditional process. In this study the mediation behaviour of two inherently different RAFT agents was investigated by the “living” free radical polymerization of model monomers via the RAFT process in homogeneous and aqueous dispersed media with the focus on differentiating between the two types of agents. To ensure that the agents were comparable a new RAFT agent had to be prepared which has not previously been documented. The efficiency of the RAFT agents was compared in terms of rate effects, the predictability of the molecular weights of the polymers, the polydispersities of the polymers and their ability to allow block copolymer formation via sequential addition of monomers. Block copolymerizations were conducted by the addition of new monomer to the already existing RAFT end-capped chains. Monomer addition was done via three different approaches; namely shot addition, feed addition and pre-swelling (in the case of emulsions). Chromatographic analysis was conducted on the resulting block copolymers via liquid chromatography at critical conditions (LCCC), and its online coupling with size-exclusion chromatography (SEC) to obtain two-dimensional information on the differences in heterogeneity of their molecular distributions. Other analyses included dynamic light scattering analysis (DLS) and transmission electron microscopy (TEM). The detailed analysis enabled the understanding of the different products that are produced via the two different classes of RAFT agent. Potential causes for the differences are discussed and possible areas for future research are highlighted. The work presented here is the most detailed investigation of this class of polymerization to date and will provide new insight for researchers working in this vibrant and important research field. / AFRIKAANSE OPSOMMING: Polimere gesintetiseer deur die gebruik van radikaal tegnieke is algemeen in ons daaglikse omgewing. Die tegniek is egter beperk deur die gebrek aan beheer oor die polimerisasie en die onvermoë om blokkopolimere te sintetiseer. Blokkopolimere beskik oor ‘n aansienlike hoeveelheid potensiele aanwendinge in gevorderde materiale en is gevolglik ‘n belangrike navorsingsgebied. Omkeerbare addisie fragmentasie ketting oordrag (OAFO) is ‘n lewende vrye radikaal proses wat die inherente nadele van die tradisionele proses oorkom. In die betrokke studie is die mediasie gedrag van twee verskillende OAFO agente bestudeer deur die lewende vrye radikaal polimerisasie van model monomere deur die OAFO proses in homogene en waterig dispersie media met die fokus op differensiering tussen die twee tipes agente. Om te verseker dat die twee agente vergelykbaar is, is ‘n nuwe OAFO agent voorberei wat tot op hede nog nie gedokumenteer is nie. Die effektiwiteit van die OAFO agente is vergelyk in terme van tempo effekte, die voorspelbaarheid van die molekulêre massa van die polimere, die polidispersiteit van die polimere en die moontlikheid om blokkopolimerisasie deur kronologiese byvoeging van monomere te fasiliteer. Blokkopolimerisasie is uitgevoer deur die byvoeging van nuwe monomeer tot die alreeds bestaande OAFO eind-groep kettings. Monomeer byvoegings is uitgevoer deur drie verskillende metodes; naamlik vulskoot addisie, voer addisie en vooraf swelling (in die geval van emulsies). Chromatografiese analise is uitgevoer op die resulterende blokkopolimere deur vloeistof chromatografie by kritieke kondisie (LC-CC) en die aanlyn koppeling met grootte-uitsluiting vloeistof chromatografie, om twee-dimensionele informasie omtrent die verskille in heterogeniteit van hul molekulere verdeling te bepaal. Verdere analise sluit dinamiese verstrooing mikroskopie en transmissie elektron mikroskopie in. Die detaileerde analise onthul die samestelling van die verskillende produkte wat geproduseer is deur die verskillende klasse van OAFO agent. Potensiele oorsake vir die verskille is bespreek en moontlike areas vir toekomstige navorsing is benadruk. Die werk hier voorgestel is die mees gedetaileerde navorsing van hierdie tipe klas van polymerisasie tot op hede en beloof nuwe insig vir navorsers betrokke in hierdie dinamiese en belangrike navorsingsveld.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The Reversible addition fragmentation chain transfer (RAFT) technique is a robust and versatile technique that enables the synthesis of polymers of controlled molecular weight and polydispersity. The application of the RAFT technique in heterogeneous aqueous media has attracted great interest in academics and industry due to it being more environmentally friendly, besides its other advantages. To date, the synthesis of well-defined high molecular weight polymers via the RAFT process under industrially relevant conditions still remains a challenge for polymer chemists. The study addresses the application of the RAFT process in heterogeneous media, namely in miniemulsion polymerization, for the synthesis of AB diblock copolymers of n-butyl methacrylate and styrene. AB diblock copolymers of high molecular weight were successfully prepared via a twostep method. In the first step, a dithiobenzoate monofunctional RAFT agent was used in bulk polymerization with the first monomer, n-butyl methacrylate. After the polymerization, the majority of the polymer chains contained the thiocarbonyl-thio RAFT agent functionality, which makes the chains potentially active for chain extension. The polymeric RAFT agent (also referred to as the starting block) obtained in the first step was chain extended in the second step, in miniemulsion, upon further addition of fresh initiator and the second monomer, styrene. The effects of the initiator/RAFT agent concentration ratio on the miniemulsion systems were investigated. The miniemulsion systems used for the high molecular weight AB diblock copolymers exhibited living features despite the high polydispersity indices. Kinetic results showed an increase in the rate of polymerization throughout the polymerization. Size exclusion chromatography (SEC) results indicated significant broadening in the molecular weight distributions and a steep increase in the polydispersity during the polymerization. It was concluded that the broad molecular weight distributions and steep increase in the polydispersity was not only related to the initiator concentration but possibly due to other factors such as inhomogeneity in the miniemulsion system and a transition in the kinetic behavior during the polymerization. Secondary particle formation emerged from kinetic data and transmission electron microscopy (TEM) results, but this were not supported by the SEC results. The effect of the use of a water-soluble initiator on the miniemulsion system was also investigated. Results indicated a similar behavioral pattern as observed in the AIBNinitiated systems, and not much improvement in terms of the molecular weight distributions and polydispersity was seen. The effect of the molecular weight of the diblock copolymers on the miniemulsion system was investigated. Poly(n-butyl methacrylate)-b-poly(styrene) diblock copolymers of lower molecular weight were synthesized via the two-step process. Kinetic results indicated a similar behavioral trend as to that of the high molecular weight diblock copolymers synthesized, however SEC chromatograms showed narrower molecular weight distributions and low polydispersity indices.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / This study concerns the polymerization of propylene both in the presence and absence of molecular hydrogen. The percentage of hydrogen used as a terminating agent in the polymerization reactions was varied from 0.1 wt% to 15.0 wt% in order to compare a variety of polymers with different percentages of hydrogen incorporated. Two ansa metallocene catalysts were used: (A) rac-[ethylene bis(indenyl)] zirconium dichloride (rac-Et(Ind)2ZrCl2) and (B) dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride (rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2). Methylaluminoxane (MAO) was used as cocatalyst for both of the two catalysts. Characterization of the polymers included using nuclear magnetic resonance spectroscopy (NMR) for information concerning the microstructure of the polymers, high temperature gel permeation chromatography (HT-GPC) for molecular weight and molecular weight distributions and differential scanning calorimetry (DSC) to investigate the melting point and crystallization behaviour of the polymers. The polypropylenes prepared with the dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride catalyst system were compared to the polypropylenes synthesized with ethylene-bis(indenyl) zirconium dichloride. In particular, the effects of hydrogen on the microstructure, molecular weight, molecular weight distribution, melting point and crystallization behaviour were investigated.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The surfmers sodium l l-rnethacryloyloxy undecanyl-I sulfate (MET) and sodium 11- crotonoyloxy undecanyl-I sulfate (CRO) were synthesized and purified. Both contain a sulfonate and polymerizable double bond connected by a hydrocarbon chain. Sodium 4-[ 11- (3-carboxypropionoyloxy)-undecyloxy] benzenesulfonate (PSA-MA) could not be synthesized successfully. MET and CRO were characterized by means of nuclear magnetic resonance spectroscopy (NMR), elemental analysis (EA), thermal gravimetric analysis (TGA), determination of the critical micelle concentration (CMC), differential scanning calorimetry (DSC), and microscopy. MET and CRO displayed a liquid crystalline behavior. MET and CRO were used in combination with poly(diallyl dimethyl ammonium chloride) to form polyelectrolyte-surfactant complexes by common precipitation in water. These complexes were redissolved in methanol and cast in films. The cast films were investigated by wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) with regard to ordered mesomorphous phases. Due to the destabilization of the lyotropic phase, little order were observed in the complexes. MET was co-polymerized with styrene and methyl methacrylate, in different proportions, by means of free radical polymerization. The co-polymers were characterized by NMR and infrared spectroscopy (Ik) and analyzed by DSC, TGA and gel permeation chromatography (GPC). All analytical techniques showed that the co-polymers were synthesized successfully. TEM indicated a fine, lamellar micro-structure. / AFRIKAANSE OPSOMMING: Die polimeriseerbare sepe, natrium-ll-metakrieloloksi-undekaniel-l sulfaat (MET) en natrium-ll-krotonieloksi-undekaniel-l-sulfaat (CRO) is berei en gesuiwer. Beide bevat 'n sulfonaat en 'n polimeriseerbare dubbelbinding wat deur 'n koolwaterstofketting verbind word. Natrium-4-[11-(3-karboksipropionieloksi)-undekieloksi]-benseensulfaat (PSA-MA) kon nie suksesvol berei word me. MET en CRO is deur middel van kernmagnetieseresonansspektroskopie (KMR), elementele-analise (EA), termiesegravimetriese analise (TOA), kritiese miselkonsentrasie (CMC), differensieelskandeerkalorornetrie (DSC) en mikroskopie gekarakteriseer. Beide MET en CRO het 'n vloei-kristalgedrag getoon. MET en CRO is met poli(diallieldimetielammoniumchloried) gereageer om polyelektrolietseepkompleks te vorm deur presipitasie uit water. Die komplekse is in metanol opgelos en films daarvan gemaak. Die films is deur wyehoek X-straal diffraksie (WAXS) en kleinhoek X-straaldiffraksie (SAXS) ondersoek om geordende mesomorfiese fases te ondersoek. As gevolg van destabilisasie van die liotropiese fase is min orde in die komplekse gevind. MET is met stireen en metielmetakrilaat deur middel van vryeradikaalpolymerisasie gekopolimeriseer. Die kopolimere is deur middel van KMR- en infrarooispektroskopie (IR), DSC, TOA en gelpermeasiechromotagrafie (OPC) ondersoek. Al hierdie analitiese metodes het die suksesvolle sintese van die kopolimere bewys. Transmissie-elektronmikroskopie het die teenwoordigheid van 'n fyn, laminere mikro-struktuur bewys.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Controlled free radical polymerisation techniques offer several practical and theoretical advantages compared to many other polymerisation techniques. Living polymerisation techniques such as anionic polymerisations require the total exclusion of impurities such as oxygen and moisture. Controlled free radical polymerisations, however, do not require such stringent methods of practice. This is very advantageous for industrial purposes. Atom Transfer Radical Polymerisation (ATRP) is a form of a controlled/living free radical polymerisation technique by which one is able to synthesize controlled architectural structures and predetermine the molecular weights of macromolecules. The monomers that were investigated for this research project include methyl methacrylate (MMA), 4-vinylpyridine (4VP) and lauryl methacrylate (LMA). The latter two monomers (4VP and LMA) are not commonly used in ATRP-mediated reactions. The synthesis of block copolymers ofMMA and LMA were attempted. The homopolymerisation of 4VP did not give the control expected when polymerising by means of ATRP. This prompted an investigation into possible side reactions that could take place with 4VP in this specific ATRP system. This included possible quatemization of 4VP with the alkyl halide initiator species. / AFRIKAANSE OPSOMMING: Beheerde vrye-radikaalpolimerisasietegnieke bied verskeie praktiese en teoretiese voordele bo verskeie ander vrye-radikaalpolimerisasietegnieke. Lewende polimerisasietegnieke soos anioniese polimerisasie, vereis die totale uitsluiting van onsuiwerhede soos suurstof en water. Beheerde vrye-radikaalpolimerisasies vereis egter nie sulke streng reaksiekondisies nie. Hierdie is baie voordelig vir industriële doeleindes. Atoomoordragradikaalpolimerisasie (ATRP) is 'n tipe beheerde/lewende vryeradikaalpolimerisasietegniek wat dit moontlik maak om die samestelling en struktuur van makromolekules asook die molekulêre massa presies te beheer. In hierdie studie is die monomere metielmetakrilaat (MMA), 4-vinielpiridien (4VP) en laurielmetakrilaat (LMA) bestudeer. Laasgenoemde twee monomere (4VP en LMA) word beskou as ongewone monomere om in ATRP-sisteme te gebruik. Daar is gepoog om blok kopolimere van MMA en LMA te sintetiseer. Die homopolimerisasie van 4VP het minder beheer gelewer as wat by beheerde vrye-radikaal sisteme soos hierdie verwag word. Na aanleiding van hierdie resultate is 'n ondersoek geloods om die moontlike newereaksies van 4VP in hierdie spesifieke ATRP-sisteem te ondersoek. Daar is gepoog om te bewys dat die alkielchloriedinisieerder verdwyn deur kwatemisasie met 4VP.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: This study describes the design, building and optimization of a fully functional preparative TREF (Prep-TREF) apparatus. This apparatus allows for the fractionation of semicrystalline polyolefins according to the crystallizability of the molecules. Various factors, such as the sample cooling rate and the effect of on-support and off-support crystallization, are investigated. The preparative TREF is used to fractionate a commercial low-density polyethylene (LOPE), two commercially available plastomers (polyethylene-l-octene copolymers), as well as blends of the LOPE and the respective plastomers. It is shown that in each case the samples fractionated by crystallizability. The fractions recovered from the Prep-TREF were characterized by CRYSTAF, OSC and NMR analysis. It is shown how the results of this preparative fractionation allow for a better understanding of the molecular heterogeneity in the LOPE and plastomers. New ways of presenting the data from the preparative fractionation, in terms of 3- dimensional plots, are also investigated. These plots offer a novel way of presenting the molecular heterogeneity in the samples in terms of the molecular crystallizability. These plots highlight features that are difficult to detect in the conventional two-dimensional plots. In conclusion, the influences of various blending ratios of LOPE and plastomer on the morphological and physical properties of the blends, such as haze, clarity, and tear-and impact strength are determined. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die ontwikkeling en optimisering van 'n ten volle funksionerende TREF. Hierdie tegniek word gebruik om polimeermengsels te fraksioneer deur gebruik te maak van die kristaliseerbaarheid van polimere. Verskeie faktore soos die afkoel spoed en die effect van met en sonder 'n ondersteuning(seesand) vir kristaliseering was ondersoek. Hierna is navorsing gedoen om 'n beter begrip ten opsigte van die meganiese, fisiese en optiese eienskappe van lae-digtheid poliëtileen (LDPE) te ontwikkel. Hierdie LDPE is met die affiniteitsreeks plastomere van die maatskappy, Dow Chemicals, gemeng om tendense in die gefraksioneerde polimere te indentifiseer. Een van Sasol se kommersiële LDPE produkte en twee van Dow Chemicals se plastomere is individueel gefraksioneer. Die mengsel van die twee ongefraksioneerde LDPE en plastomere is nog nooit voorheen op 'n molekulêre basis ondersoek nie. Dit is in hierdie studie gedoen deur van TREF gebruik te maak. Nuwe maniere is ontwikkel om data op 'n nuwe manier voor te stel deur middel van 3 Dimensionele grafieke te skep om resultate voor te stel wat andersins baie moelilik was om voor te stel in een dimensie agv die hoeveelheid data wat geinterpreteer word. Ten slotte is die invloed van die verskillende mengverhoudings van LDPE en plastomere op die morfologiese en fisiese eienskappe soos deursigtigheid, helderheid, skeur- en impaksterkte, ook ondersoek.

Thesis (DSc (Chemistry and Polymer Science))--University of Stellenbsoch, 2006. / The synthesis and characterization of a new tertiary alcohol (2-octyl-2-dodecanol) and “bushy-tailed”, hydrophobic acrylic monomer (2-octyl-dodecyl acrylate) from a 1-decene dimer (2-octyl-1-dodecene) precursor that was synthesized with metallocene technology is reported. Some preliminary applications of the newly synthesized 2-octyl-dodecyl acrylate were investigated. These applications included the use of 2-octyl-dodecyl acrylate as a reactive hydrophobe in mini-emulsion polymerizations, and as a reactive (internal) plasticizer. In an attempt to selectively dimerize 1-decene, the effect of various factors on the oligomerization of 1-decene was investigated. These factors include the following: i. Different temperatures: 5, 35, 70 and 90°C ii. Different co-catalyst [methylaluminoxane (MAO)] concentrations iii. Different catalysts: bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) and bis(cyclopentadienyl)hafnium dichloride (Cp2HfCl2) iv. Different reaction times. In all instances the final product obtained, under the abovementioned conditions, was a mixture of residual monomer, the dimer and trimer of 1-decene. These findings were corroborated with GC-MS and 1H-NMR spectroscopy. The isolation and further processing of the dimer of 1-decene (2-octyl-1-dodecene) was investigated. The efficiency, in terms of the final product-composition for the amount of catalyst used and reaction time, of Cp2ZrCl2 compared to bis(cyclopentadienyl)hafnium dichloride (Cp2HfCl2; hafnocene) as catalyst for the oligomerization of 1-decene is also reported on. The results obtained indicated that Cp2ZrCl2 is the more efficient catalyst for the oligomerization of 1-decene. The effect of different reaction times (1, 3, 6, 24 hours) on the final product-composition for the oligomerization of 1-decene was also investigated. Longer reaction times (24 hours) seemed to be excessive. A reaction time of 6 hours was optimal. The purified 1-decene dimer (2-octyl-1-dodecene) was converted to the new tertiary alcohol (2-octyl-2-dodecanol) using the oxymercuration-demercuration procedure. The 2-octyl-dodecyl acrylate was synthesized by the esterification of the tertiary alcohol with acryloyl chloride in the presence of triethylamine. The new tertiary alcohol and acrylate were characterized by FT-IR and 1H-NMR spectroscopy. Stable polymer latex particles were successfully synthesized with the novel reactive hydrophobe 2-octyl-dodecyl acrylate in the mini-emulsion polymerization of butyl acrylate, methyl methacrylate and styrene. Phase-separation experiments showed that the presence of 2-octyl-dodecyl acrylate in the dispersed phase retards Ostwald ripening. The novel acrylic monomer, 2-octyl-dodecyl acrylate, was copolymerized with styrene via conventional free radical polymerization. Both low and high molecular weight copolymers were prepared. Thermal analysis of the copolymers showed that 2-octyl-dodecyl acrylate does act as a reactive (internal) plasticizer. Blends of commercial virgin polystyrene and the synthesized low and high molecular weight copolymers were prepared. Partially miscible blends were obtained. Decreases in the glass transition temperatures of the blends compared to the virgin polystyrene were observed. The higher molecular mass styrene/2-octyl-dodecyl acrylate copolymers produced larger decreases in glass-transition temperatures.