The present thesis is focused on rational design and synthesis of π-conjugated donoracceptor-donor (D-A-D) type oligomers and D-A type copolymers. Thesis is organized in seven chapters, apart from introduction remaining six chapters are grouped into two parts (A and B). Part A deals with Chapters 2, 3, 4 and Part B contains chapters 5, 6 and 7. A brief discussion on the content of individual chapters is provided below. Chapter 1 discusses the introduction to organic solar cell with operating principles and effect of spinodal decomposition on stability of the devices is presented. The status and literature related to the improvement of life time of the organic solar cells by self-assembly approach has been explored. In addition, design and synthesis of the fluorine substituted π-conjugated organic semiconductors for n-type OFETs and OLED has been discussed. Part A This part of the thesis attempt to address some of the challenges listed below (1) Investigation of miscibility of binary components in bulk heterojunction solar cells through H-bonding approach. (2) Synthesis of new low band gap molecular semiconductors having H-bonding sites. (3) Fabrication of bulk heterojunction solar cell devices using these new molecules and exploring the photovoltaics performance. Chapter 2, donor-acceptor-donor (D-A-D) concept has been employed to design low band gap oligomers named as TTB. Barbiturate functional group has been utilized to explore the concepts of supramolecular chemistry. It is shown that, TTB molecule self-organizes via intermolecular H-bonding between barbituric acid units. Interactions between the oligothiophene subunits were also found to be important, affording nanoribbons that were observed by atomic force and transmission electron microscopy. The applicability of TTB for organic electronic applications was investigated by fabricating organic field-effect transistors (OFETs) and organic photovoltaic device. The crystalline nanoribbons were beneficial in understanding the phase morphology of PCBM and TTB blend. Chapter 3, the self-assemble property of TTB was disrupted by the substitution of methyl group on the nitrogen of the barbituric acid moiety. The optical and electrochemical properties of the new derivative have been investigated by UV-Visible spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. Further investigations on the effect of self-assembly on organic solar cells were carried out by fabricating BHJ and OFET. The results proved that the self-assembly within the donor moieties led to complete phase separation between the donor and acceptor which had an adverse effect on the photovoltaic performance. Chapter 4, the conjugation of TTB was extended by the synthesis of two new copolymers by polymerizing with two oliogothiophene (terthiophene and benzobithiophene) derivatives with different donating strength. The investigation of photophysical and electrochemical properties of copolymers were studied by varying the donating strength. As we increase the donating strength of oligothiophenes, the intramolecular charge transfer band of DA copolymers was red shifted. Further, density functional theory (DFT) calculation of these materials was carried out to get insight into their photophysical properties. Part B This part of the thesis attempt to address some of the challenges listed below (1) Investigation of fluorine substituted organic semiconductos like 2,2’ bithiazole and pheanthroimidazole. (2) Synthesis of pentafluoro phenyl appended derivatives of 2,2’ bithiazole and pheanthroimidazole. (3) Fabrication of OFETs and OLEDs using these new molecules and elucidated the device performance with molecular structure. Chapter 5, pentafluorophenyl appended 2,2’-bithiazole derivatives were synthesized. The single crystal x-ray diffraction studies shows the unusual strong type-II F•••F interactions within the distance of 2.668 Å, at an angle of 89.14° and 174.15°. It also shows the usual type-I F•••F interaction within the distance of 2.825Å, at an angle of 137.38° and 135.93°. Upon bromination type-II Br•••Br interaction was observed and the packing was further stabilized by S•••Br interactions. The conjugation was further extended with different aromatic and heteroaromatic substituents and synthesized the star shaped structure. The band gap as well as the electronic energy levels was tuned by substituting various aromatic and heteroaromatic substituents. These star shaped derivatives shows electron mobilities in the order of 10-4 to 10-3cm2/Vs. Chapter 6, Novel D-A copolymers were synthesized by Stille condensation of electron acceptor fluorinated phenanthroimidazole with electron donors like terthiophene and benzobithiophene. Prior to that insoluble pentafluoro phenyl phenanthroimidazole was Nalkylated in presence of DMF which concurrently resulted in C-F activation of the pentafluoro phenyl moiety. As we increase the donor strength from benzobithiophene to terthiophene the absorbance spectra was red shifted from 446 nm to 482 nm in solution and 455 nm to 484 nm in solid state. The band gap of these copolymers was found to be 2.4 eV for PIBDT and 2.2 eV for PIDHTT from the absorbance spectra. The photoluminescence data shows that these materials are promising for the yellow colour as well as orange colour displays, of narrow wavelength range (FWHM 40 nm for PIBDT and 35 nm for PIDHTT), which can be achieved just by the manipulation of donor moieties in the copolymers. The preliminary electroluminiscence data shows high brightness of 888cd/m2 (orange luminescence) for PIDHTT and 410cd/m2 (yellow luminescence) for PIBDT. Chapter 7, Acenaphtho[1,2-b]quinoxaline based donor–acceptor type low band gap conjugated copolymers were synthesized by Stille coupling reaction with the corresponding oligothiophene derivatives. The optical properties of the copolymers were characterized by ultraviolet-visible spectrometry while the electrochemical properties were determined by cyclic voltammetry. The band gap of these polymers was found to be in the range of 1.8-2.0 eV as calculated from the optical absorption band edge. The intense charge transfer band in absorption spectra shows the significant effect of acceptor in the copolymers. X-ray diffraction measurements show weak π–π stacking interactions between the polymer chains. The OFET devices fabricated using these co-polymers showed dominant p-channel transistor behavior with the highest mobility of 1×10-3cm2/Vs.

Η αλληλεπίδραση μεταξύ συνθετικών πολυηλεκτρολυτών και ιόντων στοιχείων μετάβασης, και κατ επέκταση η δημιουργία συμπλόκου μεταξύ τους, έχει τύχει μεγάλου ενδιαφέροντος από τους ερευνητές τις τελευταίες δεκαετίες. Αυτό το ενδιαφέρον αποδίδεται στις μοναδικές ιδιότητες των σχηματιζόμενων συμπλοκών, καθώς μπορούν να χρησιμοποιηθούν σε διάφορα πεδία όπως στην ιατρική, την τεχνολογία και τις βιομηχανίες τροφίμων ή την αποκατάσταση των περιβαλλοντολογικών προβλημάτων. Σε αυτή την εργασία προχωρήσαμε στη παρασκευή των συμπολυμερών P(EV2-PDMAM) που αποτελείται από ένα συμπολυμερές (EV2) του αιθυλενίου με το μηλεϊνικό οξύ ως σκελετό, επί των οποίων έχουν εμβολιαστεί αλυσίδες πολυ(Ν,Ν-διμεθυλακρυλαμιδίου) (PDMAM). Η γραμμομοριακή σύσταση των συμπολυμερών, εκφρασμένη σε δομικές μονάδες DMAM, ήταν 25, 50 και 75%. Η φυσικοχημική μελέτη της αλληλεπίδρασης των ιόντων δισθενούς χαλκού με τα συμπολυμερή P(EV2-PDMAM) πραγματοποιήθηκε με μια σειρά τεχνικών όπως η ιξωδόμετρα, η pHμετρία και η φασματοσκοπία υπεριώδους-ορατού (UV-vis). Η δημιουργία συμπλόκου οδηγεί σε σημαντική συρρίκνωση της πολυμερικής αλυσίδας, όπως διαπιστώθηκε από τη σημαντική μείωση του ανηγμένου ιξώδους. Από την pHμετρική μελέτη παρατηρούμε ότι καθώς αυξάνεται η συγκέντρωση των ιόντων δισθενούς χαλκού μειώνεται σημαντικά η τιμή του pH. Τέλος, η συμπλοκοποίηση των ιόντων Cu2+ με τα συμπολυμερή διαπιστώθηκε και με φασματοσκοπία υπεριώδους-ορατού, καθώς η κορυφή απορρόφησης των ιόντων Cu2+ μετατοπίζεται και ενισχύεται σημαντικά, σε σχέση με την αντίστοιχη συμπεριφορά των ελεύθερων ιόντων Cu2+. / The interaction between synthetic polyelectrolytes with transition metal ions leading to complex formation has attracted the research interest during the last decades. This interest is attributed to the unique properties of the complexes formed, as they can find uses in many fields, like medicine, food industries or remedation of environmental problems. In this work we proceeded to the synthesis of comb-like copolymer, denoted P(EV2-PDMAM). These copolymers are based on a poly(ethylene-co-maleic acid) backbone (EV2), onto which poly(N,N-dimethylacrylamide), (PDMAM) side chains were grafted. The molar composition of the copolymers, expressed in DMAM structural units was 25, 50 and 75%. The physicochemical study of the interaction of Cu2+ with the P(EV2-PDMAM) was performed using a series of techniques, such as viscometry, potentiometry and UV-vis spectrometry. Complex formation leads to a vey significant shrinkage of the polymer chain, as it is revealed by the decrease of the reduced viscosity. The potentiometric study revealed that the pH of the aqueous polymer solution decreases considerably upon increasing the concentration of Cu2+ ions. Finally, the UV-vis investigation also verified the polymer-Cu2+ complexation, since the absorption peak of Cu2+ ions shifts towards lower wavelengths and the intensity of the band is significantly enhanced as compared to the respective properties of free Cu2+ ions.

Applications of conjugated polymer (CPs) in optoelectronic devices are critically depend on nature of thin film morphology. In thin film of CPs, the distribution of conjugation length is highly heterogeneous because of conformational defects, distortions of polymer chain and aggregates. A greater understanding of the self-assembly properties of polymer in solution, in particular control over aggregation leads to richer description of electronic properties and hence reproducible fabrication of thin film devices. Recently, chiral CPs have attracted profound interest because of their promising chiroptical properties in thin films and easy control over the selective agglomeration process. In this thesis, we have investigated the role of chiral side-chains on a series of thiophene diketopyrrolopyrrole (TDPP)-benzodithiophene (BDT) based copolymers. Chiral 3,7-dimethyloctyl chain was introduced as an asymmetric chain to incorporate chirality on one of the repeating unit (TDPP) of copolymers. Two polymers with side-chains of identical chirality (S),(S)-PTDPP-BDT; (R),(R)-PTDPP-BDT and a third polymer with similar side-chains of opposite chirality (R),(S)-PTDPP-BDT were synthesized. The chiroptical properties were investigated by UV-visible and circular dichroism (CD) spectroscopy. Figure 1: The structure of the TDPP-BDT copolymers. The copolymers dissolved in a good solvent (e.g. chloroform, chlorobenzene) in which polymers adopts random coil conformation, no chiral response has been observed. However, a critical addition of non-solvent (methanol), the copolymers stack in a chiral fashion and leads to typical bisignate Cotton effects. It is noteworthy that the two polymers, (S),(S)-PTDPP-BDT and (R),(R)-PTDPP-BDT exhibiting a nearly ideal mirror-image relationship in CD spectra (Figure 2a) whereas the (R),(S)-PTDPP-BDT lacks chiropticity even with the addition of methanol. The aggregation induced CD phenomena are dependent on the temperature of solution and do not exhibit reversibility in a heating-cooling cycle. Figure 2: (a) The mirror image Cotton effects of (S),(S)-PTDPP-BDT and (R),(R)-PTDPP-BDT (b) No CD signal was observed for the (R),(S)-PTDPP-BDT polymer. Figure 3: The variation of (a) UV-vis and (b) CD spectra of (R),(R)-PTDPP-BDT polymer with thickness of the solid film. To investigate the role of thickness and annealing temperature on optical and chiroptical properties of polymer films, thin films were prepared using drop-casting method from a solution of chlorobenzene. Both the polymer showed gradual enhancement of CD signal with the increase of film thickness but we did not see any such order with temperature (Figure 3). Figure 4: The morphology observed for the film by (a) AFM; (b); (c) FESEM. The thin film morphology of polymers is characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) (Figure 4). AFM studies show the polymer molecules self-assembled and formed interconnected nanofibers. Whereas FESEM images clearly revealed that, the nanofibers of polymers are predominantly stack in a chiral fashion and mimic a one-handed helix which leads to bisignate Cotton effects. The (S),(S)-PTDPP-BDT and (R),(R)-PTDPP-BDT form fibers with opposite handedness whereas (R),(S)-PTDPP-BDT do not have such preferred handedness. The research described in this thesis aims to explore the role of chiral side-chains to impose chiral stacking and hence resulting chiral expression. Chirality in this class of polymers may endows them promising optoelectronic properties. (For figures pl see the abstract pdf file)

Block copolymers are commercially significant and fundamentally interesting class of polymeric materials. The ability to undergo interfacial thermodynamics-controlled microphase separation from a completely disordered state in the melt to a specifically defined ordered structure through self-organization makes the block copolymers based materials unique. Block copolymer are strongly replacing many of the commercially available polymers due to their unique microstructure and properties. The most practical interests of block copolymers lie in the area of thermoplastic elastomers (TPEs). The objective of the present thesis work is to developing novel roots for enhancing the physical and mechanical properties in block copolymer and multigraft copolymers. Initially the properties are tailored by controlling chemical architecture at synthesis level and by selective blending at production level. This gives an easy access for improvement of the material properties and this is one of my major tasks in the present research modules. Further the block copolymer based TPEs are cross-linked in presence of electron beam (EB) radiation for developing materials with superior properties. The electron beam radiation has the ability to alter material parameters at molecular level for enhancing the macroscopic properties. The desirable physical and chemical properties can be easily attained by varying the radiation beam parameters. In addition to that, controlling the material at nanometer scale is one of the greatest challenges for current nanocomposite research. In elastomeric materials it is very prominent to fill the rubber matrix with nano particles from carbon or silica by melt mixing technique for enhancing the material properties. Other than conventional melt mixing technique, sol–gel processing is also a versatile technique, which making it possible to produce a wide variety of materials and to provide existing materials with novel properties. A combination of in situ sol-gel reaction with electron beam cross-linking in TPEs from triblock copolymer has been demonstrated for the first time as one of the novel nanocomposite system in this work. The main advantage of this system lies in controlling the material behaviour by finely tuning the size of silica nano particle generated inside TPE during in situ sol-gel reaction. Finally, the various roots employed for enhancing the material behaviour in block copolymers in the above research module were secussfully employed on super elastic multigraft copolymers for improving their strength withour sacrificing the super elastic nature.

This thesis describes the synthesis and application of a new series of amphiphilic graft copolymers with a hydrophobic polyolefin backbone and pendent hydrophilic poly(ethylene glycol) (PEG) grafts. These copolymers are synthesized by ruthenium benzylidene-catalyzed ring-opening metathesis polymerization (ROMP) of PEG-functionalized cyclic olefin macromonomers to afford polycyclooctene- graft -PEG (PCOE- g -PEG) copolymers with a number of tunable features, such as PEG graft density and length, crystallinity, and amphiphilicity. Macromonomers of this type were prepared first by coupling chemistry using commercially available PEG monomethyl ether derivatives and a carboxylic acid-functionalized cycloctene. In a second approach, macromonomers possessing a variety of PEG lengths were prepared by anionic polymerization of ethylene oxide initiated by cyclooctene alkoxide. This methodology affords a number of benefits compared to coupling chemistry including an expanded PEG molecular weight range, improved hydrolytic stability of the PEG-polycyclooctene linkage, and a reactive hydroxyl end-group functionality for optional attachment of biomolecules and probes. The amphiphilic nature of these graft copolymers was exploited in oil-water interfacial assembly, and the unsaturation present in the polycyclooctene backbone was utilized in covalent cross-linking reactions to afford hollow polymer capsules. In one approach, a bis -cyclooctene PEG derivative was synthesized and co-assembled with PCOE-g-PEG at the oil-water interface. Upon addition of a ruthenium benzylidene catalyst, a cross-linked polymer shell is formed through ring-opening cross-metathesis between the bis -cyclooctene cross-linker and the residual olefins in the graft copolymer. By incorporating a fluorescent-labeled cyclooctene into the graft copolymer, both oil-water interfacial segregation and effective cross-linking were confirmed using confocal laser scanning microscopy (CLSM). In a second approach, reactive functionality capable of chemical cross-linking was incorporated directly into the polymer backbone by synthesis and copolymerization of phenyl azide and acyl hydrazine-functional cyclooctene derivatives. Upon assembly, these reactive polymers were cross-linked by photolysis (in the phenyl azide case) or by addition of glutaraldehyde (in the acyl hydrazine case) to form mechanically robust polymer capsules with tunable degradability ( i.e. non-degradable or pH-dependent degradability). This process permits the preparation of both oil-in-water and water-in-oil capsules, thus enabling the encapsulation of hydrophobic or hydrophilic reagents in the capsule core. Furthermore, the assemblies can be sized from tens of microns to the 150 nm - 1 µm size range by either membrane extrusion or ultrasonication techniques. These novel capsules may be well-suited for a number of controlled release applications, where the transport of encapsulated compounds can be regulated by factors such as cross-link density, hydrolytic stability, and environmental triggers such as changes in pH.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Polyurethanes (PUs) are finding increasing application and use in many industries due to their advantageous properties, such as a wide range of flexibility combined with toughness, high chemical resistance, excellent weatherability, and very low temperature cure. PUs do however have some disadvantages, for instance, PU is considered an expensive polymer, especially when considered for solvent based adhesives. A motivation for this study was to consider a largely unstudied area of PU chemistry by combining PUs with polyacrylates. Polyacrylates are well known adhesives and can carry specific functionality, but have the disadvantage that their flexible backbones impart limited thermal stability and mechanical strength. In this study PU was incorporated into acrylates in an effort to obtain acrylate-g-urethanes with good properties. The mode of incorporation chosen was urethane macromonomers (UMs), a hardly mentioned substance in literature, yet one deserving investigation. UMs having different urethane chain lengths (X) were synthesized by the polyaddition polymerization of toluene diisocyanate (TDI) and ethylene glycol (EG) by the prepolymer method, which was terminated by 2-hydroxy ethyl methacrylate (HEMA) and isopropanol. The UMs were characterized by Fourier-transform infrared spectroscopy (FTIR), proton NMR (1H NMR), carbon NMR (13C NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Various percentages of the respective UMs (0-40 wt % according to acrylate monomers) were then incorporated into methyl methacrylate (MMA) and into normal butyl methacrylate (n-BMA) backbones via solution free radical copolymerization. The resulting methyl methacrylate-urethane graft copolymers (PMMA-g-urethane) and normal butyl methacrylate-urethane graft copolymers (n-PBMA-g-urethane) were characterized by GPC, 1H NMR and 13C NMR, FTIR, TGA, and DMA. Phase separation between the urethane segment and acrylate segment in the yield of graft copolymerization products was investigated by DMA and transmission electron microscopy (TEM). As the concentration of the UMs in the free radical copolymerization feed increased, lower yields of both graft copolymers PMMA-g-urethane and n-PBMA-g-urethane were observed and more UM was incorporated into the PMMA and n-PBMA backbones. It also was found that the thermal stability of the PMMA-g-urethane and n-PBMA-gurethane copolymers increased with increasing UM concentration. DMA results showed that in most graft copolymer products the two respective component parts of PMMA-g-urethane or n-PBMA-g-urethane were completely compatible as only one Tg was observed. Two glass transitions, at temperatures of 22.0 and 76.0 oC, corresponding to the n-PBMA and urethane moieties, were observed when the chain length of the UMs was increased from X=4 to X=32 [the amount of this UM used in the copolymerization feed was increased to 40%, and microphase separation was indicated].

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Chemical and molecular tagging agents have illustrated their diversity in a number of different applications. One of the most significant applications includes the use of chemical tagging agents for product registration in industry. Industrial enterprises producing good products need to ensure product authenticity to prevent duplication through piracy and unscrupulous industrialists. Fluorescent probes are chemical compounds that satisfy most of the technical and commercial aspects that are required to be excellent tagging agents. They are generally quick to synthesize, do not affect the product integrity, display little or no impact on the uses of the product or the environment and they can be identified by relatively simple detection procedures. The aim of the present study was to synthesize fluorescent polymers as tagging agents for the paint industry. 7-Hydroxy-2H-chromen-2-one (A1) and 7-hydroxy-4-methyl-2H-chromen-2-one (B1), commercially available fluorescent hydroxyl compounds, were selected as the starting materials. An esterification reaction resulted in the production of 2-oxo-2H-chromen-7-yl acrylate (A2) and 4-methyl-2-oxo-2H-chromen-7-yl acrylate (B2), which are acrylic-type monomers that were required for polymerisation. Studies showed that fluorescence was maintained during the esterification. Copolymers poly(MMA-co-A2), poly(MMA-co-B2), poly(BA-co-A2) and poly(BA-co-B2), synthesized via homogeneous free radical initiated copolymerisation, revealed how copolymer compositions were affected by the feed compositions and the pattern of monomer incorporation over time. This was investigated by following individual monomer consumption rates by 1H-NMR spectroscopy. Fluorescence studies revealed that the fluorescence behaviour of A2 and B2 was maintained during the copolymerisation. Latex particles, with fluorescent behaviour, were synthesized via in situ miniemulsion polymerisation. High molecular weight copolymers with monodisperse particle sizes (nm range) were obtained. A bench-top UV lamp and UV-reflectance studies confirmed the fact that fluorescent latex particles can be identified and quantified respectively, when dispersed in paints that are either free of titanium dioxide or paints that contain titanium dioxide. / AFRIKAANSE OPSOMMING: Die diversiteit van chemiese en molekulêre merkers in ‘n verskeidenheid van toepassings is al telkemale geïllustreer. Een van die mees belangrike toepassings in die industrie is die gebruik van chemiese merkers vir produkregistrasie. Industrieë wat goeie produkte verskaf moet die egtheid van hul produkte kan verseker deur duplikasie via nadruk (Eng: piracy) deur ander te voorkom. Fluoresserende merkers is chemiese stowwe wat aan die meeste van die tegniese en kommersiële vereistes voldoen om as uitstekende merkers te dien. Die sintese van die merkers is gewoonlik nie tydrowend nie, beïnvloed nie die integriteit van die produk nie, het min of geen impak op die gebruike van die produk of die omgewing en kan deur relatief eenvoudige prosedures bepaal word. Die doel van hierdie studie was die sintese van fluoresserendepolimere om as merkers in die verfindustrie te dien. 7-Hidroksie-2H-chromen-2-oon (A1) en 7-hidroksie-4-metiel-2H-chromen-2-oon (B1), fluoresserende hidroksielverbindings wat kommersieël beskikbaar is, is gekies as uitgangstowwe vir die bereiding van die merkers in hierdie studie. ‘n Esterifikasie-reaksie het gelei tot die produksie van 2-okso-2H-chromen-7-ielakrilaat (A2) en 4-metiel-2-okso- 2H-chromen-7-ielakrilaat (B2). Hierdie produkte is tipiese akrilaat-tipe monomere wat benodig word vir polimerisasie. Ondersoeke het getoon dat fluoressensie behoue tydens esterifikasie gebly het. Die kopolimere poli(MMA-ko-A2), poli(MMA-ko-B2), poli(BA-ko-A2) en poli(BA-ko-B2) is deur homogene vry-radikaal-geïnisieerde kopolimerisasie gesintetiseer. Daar is vasgestel hoe die kopolimeersamestelling geaffekteer is deur die samestelling van die reagense (Eng: feed composition) en die patroon van monomeer inkorporasie met tyd. Dit was ondersoek deur die tempo van verbruik van die individuele monomere d.m.v. 1H-KMR spektroskopie te bepaal. Daar is verder vasgestel dat die fluoressensie van A2 en B2 gedurende kopolimerisasie behoue gebly het. Latekspartikels, met fluoressensie gedrag, is via in-situ mini-emulsie-polimerisasie gesintetiseer. Hoë molekulêre massa kopolimere met monodisperse partikelgroottes (in die order van nanometers) is verkry. Deur van ‘n UV-lamp en UV-refleksie studies gebruik te maak is daar bepaal dat fluoresserende latekspartikels in polimere, in verf - wat of titaniumdioksied bevat of geen titaniumdioksied bevat nie -, beide geïdentifiseer and gekwantifiseer kan word.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Synthesis of a series of poly (methylmethacrylate)-graft-poly (styrene) polymer was carried out via free radical polymerization of methylmethacrylate and polystyrene macromonomers. The macromonomers were synthesized via living anionic polymerization techniques. Two series of macromonomers where synthesized with different polymerizable end group functionalities, by termination with p-vinyl benzyl chloride and 3-(dimethyl chloro silyl) propyl methacrylate. The branch density was varied by controlling the composition feed ratio of the macromonomers to comonomer. Liquid chromatographic techniques were used to fully characterize the chemical composition and branch distributions of the graft polymer. Liquid chromatography under critical conditions of adsorption of styrene coupling with Fourier Transform Infrared Spectra was used to investigate the chemical composition and distribution of the branches in the graft. Physical properties of the graft copolymers such as Tg and free volume were determined using differential scanning calorimetry and positron lifetime spectrometry respectively. The relationship between the chemical composition and the graft copolymer properties such as Tg and free volume were investigated. The results show that for long chain macromonomers phase segregation occurs in the graft copolymers. In the case of shorter chain macromonomers at low content no phase segregation is observed and the macromonomers have an antiplasticization effect on the graft polymers.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Block copolymers are very interesting materials but they are quite complex. During polymer synthesis only a certain amount of control can be enforced. As copolymers are made up of two or more different homopolymer segments, and therefore have different end group possibilities, varying block lengths and block sequences, they have complex structures and are therefore difficult to analyse. Different techniques exist by which polymers can be analysed to determine the aforementioned distributions. In order to achieve a complete characterisation of a polymer structure, it is best to first use a separation technique to fractionate the polymer into more homogeneous fractions, and then use identification techniques to analyse these fractions. Polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers were investigated using liquid chromatography at the critical conditions (LCCC) of the copolymers' corresponding homopolymers, two-dimensional liquid chromatography (2D-LC) and FTIR. The block copolymers were analysed using the established LCCC of PS but it was found that even though separation of PS homopolymer and copolymer was obtained, PS blocks of the copolymers contributed to some extent to the retention of the PEO blocks. Some of the block copolymer samples were fractionated at the established critical conditions of PS. These fractions were qualitatively and quantitatively analysed using FTIR spectroscopy. The settings for the 2D-LC analysis were established, using LCCC of PS as the first dimension and as the second dimension SEC, using DMF as eluent. DMF was a suitable solvent to be used for the second dimension because PS, PEO and PS-b-PEO exhibited good solubility in this solvent. THF did not dissolve the block copolymers completely. The same solvent system as used for LCCC of PS was used for LCCC of PEO, but the critical conditions correspond to a different solvent composition. The block copolymers were analysed using the established LCCC of PEO but it was found that even though separation of PEO homopolymer and copolymer was obtained, the PEO blocks of the copolymers contributed to some extent to the retention of the PS blocks. Some of the block copolymer samples were fractionated at the established critical conditions of PEO. These fractions were qualitatively and quantitatively analysed using FTIR spectroscopy. The settings for the 2D-LC analysis were established, using LCCC of PEO as the first dimension and as the second dimension SEC using DMF as eluent was used. Lastly, qualitative and quantitative analyses of the block copolymers were carried out using FTIR spectroscopy. / AFRIKAANSE OPSOMMING: Alhoewel blokkopolimere baie interessante verbindings is, is hulle redelik ingewikkeld. Gedurende die kopolimerisasiereaksie kan daar net 'n sekere mate van kontrole behaal word. Aangesien kopolimere uit twee of meer homopolimeersegmente, met verskillende end-groep moontlikhede, bloklengtes en blokvolgordes bestaan, is dit baie moeilik om hierdie verbindings te analiseer. Verskillende tegnieke kan gebruik word vir die analise van polimere en die bepaling van bogenoemde verspreidings. Ten einde 'n polimeerstruktuur volledig te karakteriseer is die beste manier om eers 'n skeidingstegniek te gebruik om die polimeer in meer homogene fraksies te fraksioneer en dan daarna hierdie fraksies te analiseer. Polistireen-blok-poli(etileenoksied) (PS-b-PEO) kopolimere is ondersoek deur gebruik te maak van vloeistofchromatografie by kritiese kondisies (LCCC) van die kopolimeer se ooreenkomstige homopolimere; twee-dimensionele vloeistofchromatografie (2D-LC) en FTIR. Die blokkopolimere is gekarakteriseer deur gebuik te maak van bevestigde LCCC van PS. Daar is egter gevind dat alhoewel skeiding van die PS homopolimeer en die kopolimeer behaal is, PS blokke van die kopolimere in 'n mate bygedra het tot die retensie van die PEO blokke. Sommige van die blok-kopolimeermonsters is gefraksioneer by die bepaalde kritiese kondisies van PS. Hierdie fraksies is kwalitatief en kwantitatief geanaliseer deur gebruik te maak van FTIR spektroskopie. Die stellings vir die 2D-LC analise is bepaal deur gebruik te maak van LCCC van PS as die eerste dimensie en SEC as die tweede dimensie, met DMF as elueermiddel. DMF was 'n geskikte oplosmiddel vir die tweede dimensie aangesien PS, PEO en PS-b-PEO goed oplosbaar is daarin. Die blokkopolimere was nie volledig oplosbaar in THF nie. Dieselfde oplosmiddelsisteem soos gebruik vir die LCCC van PS is gebruik vir die LCCC van PEO, maar die kritiese kondisies stem ooreen met 'n ander oplosmiddelsamestelling. Die blokkopolimere is geanaliseer deur gebruik te maak van die bevestigde LCCC van PEO, maar daar is bevind dat alhoewel skeiding van die PEO homopolimeer en kopolimeer behaal is, die PEO blokke van die kopolimere in 'n mate bygedra het tot die retensie van die PS blokke. Sommige van die blokkopolimeermonsters is gefraksioneer by die bevestigde kritiese kondisies van PEO. Hierdie fraksies is kwalitatief en kwantitatief geanaliseer deur gebruik te maak van FTIR spektroskopie. Die stellings vir die 2D-LC analise is bepaal deur gebruik te maak van LCCC van PEO as die eerste dimensie en SEC as die tweede dimensie, met DMF as elueermiddel. Laastens is kwalitatiewe en kwanitatiewe analises van die blokkopolimere m.b.v. FTIR spektroskopie uitgevoer.

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The main objective of this project was the controlled synthesis of graft copolymers via a thiol-ene addition mechanism. The Reversible Addition-Fragmentation chain Transfer (RAFT) process was used in all polymerization reactions with the aim to achieve a certain degree of control over the molecular weight. Several synthetic steps were required in order to obtain the final graft copolymer and each step was investigated in detail. Firstly, two RAFT agents (cyanovaleric acid dithiobenzoate and dodecyl isobutyric acid trithiocarbonate) were synthesized to be used in the various polymerization reactions of styrene and butyl acrylate. This was done successfully and the RAFT agents were used to synthesize low molecular weight polystyrene branches of the graft copolymer. Different molecular weights were targeted. It was found that some retardation phenomena were present especially at high RAFT agent concentrations. The polystyrene branches that were synthesized contained RAFT end-groups. Various pathways were explored to modify these RAFT end-groups to form thiol end-groups to be used in the thiol-ene addition reaction during the grafting process. The use of sodium methoxide for this purpose proved most successful and no evidence of the formation of disulfide bridges due to the initially formed thiols was detected. Allyl methacrylate (AMA) was chosen as monomer to be used for the synthesis of the polymer backbone because it has two double bonds with different reactivities. For the first time, RAFT was used to polymerize AMA via the more reactive double bond to obtain linear poly(allyl methacrylate) (PAMA) chains with pendant double bonds. However, at higher conversions, gelation occurred and the molecular weight distributions were uncontrolled. NMR was successfully used to study the tacticity parameters of the final polymer. Finally, the synthesis of the graft copolymer, PAMA-g-polystyrene, was carried out by means of the “grafting onto” approach. The thiol-functionalized polystyrene branches were covalently attached to the pendant double bonds of the PAMA polymer backbone via a thiol-ene addition mechanism in the presence of a free radical initiator. A Multi- Angle Laser Light Scattering (MALLS) detector was utilized in conjunction with Size- Exclusion Chromatography (SEC) to obtain molecular weight data of the graft copolymer. The percentage grafting, as determined by 1H-NMR, was low. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie projek is die beheerde sintese van ‘n entkopolimeer via ‘n merkaptaan-een addisiereaksie. Die sogenaamde “Reversible Addition-Fragmentation chain Transfer” (RAFT) proses is in al die polimerisasiereaksies gebruik met die doel om ‘n mate van beheer oor die molekulêre massa van die polimere te verkry. Verskeie stappe (waarvan elkeen ten volle ondersoek is) was nodig om die finale entkopolimeer te verkry. Eerstens is twee RAFT-agente (sianovaleriaansuur ditiobensoaat en dodekielisobottersuur tritiokarbonaat) gesintetiseer vir gebruik in verskeie polimerisasiereaksies van stireen en butielakrilaat. Hierdie stap was suksesvol en die RAFT-agente is toe gebruik vir die sintese van lae molekulêre massa polistireensytakke vir die entkopolimeer. Die molekulêre massas van die sytakke is gevarieer en daar is gevind dat vertragings in die polimerisasiereaksies voorgekom het, veral by hoë konsentrasies van die RAFT-agente. Die polistireensytakke wat gemaak is, besit almal ‘n RAFT-eindgroep. Verskeie roetes is bestudeer ten einde die RAFT-eindgroepe tot merkaptaan-eindgroepe te modifiseer om sodoende tydens ‘n merkaptaan-een addisiereaksie gebruik te word. Die gebruik van natriummetoksied was hier die suksesvolste en daar was geen teken van die vorming van disulfiedbrûe as gevolg van die oorspronklik gevormde merkaptane nie. Allielmetakrilaat (AMA) is gekies as die monomeer wat gebruik sou word vir die sintese van die polimeerruggraat omdat die monomeer twee dubbelbindings met verskillende reaktiwiteite besit het. Vir die eerste keer is RAFT gebruik vir die polimerisasie van AMA via die meer reaktiewe dubbelbinding om lineêre poli(allielmetakrilaat) (PAMA) kettings met dubbelbindings in die sygroepe te verkry. Gelvorming en onbeheerde molekulêre massaverspreiding het egter by hoër monomeeromsettings voorgekom. KMR is susksekvol gebruik om die taktisiteitsparameters van die finale polimeer te bestudeer. Ten slotte is die sintese van die entkopolimeer, PAMA-g-polistireen, uitgevoer deur die aanhegting van voorafgevormde sytakke. Die polistireensytakke met die merkaptaaneindgroepe is kovalent geheg aan die dubbelbindings in die sygroepe van die PAMA-polimeerruggraat via ‘n merkaptaan-een addisiemeganisme in die teenwoordigheid van ‘n vrye radikaalinisieerder. ‘n Kombinasie van gelpermeasiechromatografie en multi-hoeklaserligverstrooiing is gebruik om die molekulêre massa van die entkopolimeer te bepaal. Die persentasie sytakke soos bepaal deur 1H-KMR was laag.