by Woo Ka Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 61-63). / Abstract --- p.i / Acknowledgment --- p.ii / Contents --- p.iii / Abbreviations --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter 1 --- Introduction --- p.1 / Chapter 2. --- Theoretical background / Chapter 2.1 --- Static light scattering for homopolymer --- p.5 / Chapter 2.2 --- Static light scattering for copolymer --- p.16 / Chapter 2.3 --- Dynamic light scattering --- p.19 / Chapter 2.4 --- Modified method for copolymer --- p.28 / Chapter 3. --- Experimental / Chapter 3.1 --- Preparation of PET-PCL --- p.31 / Chapter 3.2 --- Preparation of solution for LLS --- p.31 / Chapter 3.3 --- Refractive index increment measurement --- p.32 / Chapter 3.4 --- Laser light scattering instrumentation --- p.35 / Chapter 4. --- Results and Discussion --- p.36 / Chapter 5. --- Conclusion --- p.60 / Chapter 6. --- References --- p.61

by Wong Tak Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 74-77). / Contents --- p.i / Acknowledgments --- p.iii / Abstract --- p.iv / Abbreviations --- p.v / Chapter Chapter 1. --- Introduction / Chapter 1.1. --- General background on conducting polymers and oligomers --- p.1 / Chapter 1.2. --- Conjugated oligomers and polymers --- p.3 / Chapter 1.2.1 --- Theory of conducting polymers / Chapter 1.2.2 --- Oligo- and poly-(p-phenylene)s / Chapter 1.2.3 --- Oligo and poly(phenylenevinylene)s / Chapter 1.2.4 --- Oligo and poly(phenylenethynylene)s / Chapter 1.3. --- Synthesis and solubilization of structurally rigid conjugated oligomers by dendritication --- p.19 / Chapter 1.4. --- Introduction of dendrimer chemistry --- p.20 / Chapter Chapter 2. --- Results and discussion / Chapter 2.1. --- An accelerated approach to the synthesis of oligo(phenylenevinylene)s -preparation of the propagating dimeric unit72 --- p.25 / Chapter 2.2. --- Synthesis of the polyether dendritic fragments --- p.29 / Chapter 2.3. --- Attempted coupling reactions between the polyether dendrimer and the propagating unit72 --- p.32 / Chapter 2.4. --- Synthesis and characterization of dendritic-solubilized oligo-(phenylenethynylene)s (OPE) --- p.34 / Chapter 2.4.1 --- Synthesis of conjugated propagating units / Chapter 2.4.2 --- Characterization of conjugated propagating units / Chapter 2.5. --- Synthesis and characterization of dendritic-solubilized oligo-(phenylenethynylene) fragments dendrimerized at one end --- p.39 / Chapter 2.5.1 --- Synthesis / Chapter 2.5.2 --- Characterization / Chapter 2.6. --- Synthesis and characterization of oligo(phenylenethynylene)s dendrimerized at both ends --- p.43 / Chapter 2.6.1 --- Synthesis / Chapter 2.6.2 --- Purification and characterization / Chapter 2.6.3 --- Solubility and physical appearance / Chapter Chapter 3. --- Summary --- p.49 / Chapter Chapter 4. --- Experimental section --- p.50 / References --- p.74 / List of spectra --- p.78

No description available.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / Hybrid graft copolymers of polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) were synthesised. PDMS macromonomers were synthesised anionically from the cyclic D3 monomer. This living polymerisation was terminated with a [3- (methacryloxy)propyl]-dimethylchlorosilane terminating agent which resulted in the functionalised macromonomer. These PDMS macromonomers and MMA monomer were copolymerised to form PMMA-g-PDMS hybrid copolymers by conventional free radical reactions. Synthesised and commercial methacryloxy-functionalised PDMS macromonomers having a range of molar masses were copolymerised with MMA to form graft copolymers of various chemical compositions. PDMS content in the graft copolymers could be varied by the amount of PDMS incorporated into the copolymer as well as by varying the length of the PDMS side chains. Size exclusion chromatography (SEC) results confirmed low PDI’s for the PDMS macromonomers synthesised anionically. NMR studies allowed characterisation of the synthesised PDMS macromonomers and PMMA-g-PDMS copolymers. It also allowed the determination of relative ratios of PMMA:PDMS in the graft copolymers. Gradient elution chromatography (GEC) was used successfully to monitor the presence and removal of the PDMS macromonomer from the graft copolymer products. The influence of PDMS content of the graft copolymers on retention time was also evaluated using this technique. Two dimensional chromatography confirmed the formation of PMMA-g-PDMS copolymer as well as PMMA homopolymer during some of the grafting reactions. GEC in the first dimension was coupled to SEC in the second dimension. PAS-FTIR studies allowed chemical characterisation of the graft copolymer and confirmed surface segregation of the PDMS. Atomic force microscopy (AFM) was also used to study the surface segregation of PDMS and looked at the relationship between surface polarity and increasing PDMS content. The study showed the effect of thermal treatment on the surface morphology of the hybrid polymers. Corona treatment was used to modify the surface structure of the graft copolymer films. Contact angle studies provided evidence of hydrophobic loss and recovery after corona for the hybrid polymer materials containing PDMS. This is one of the first reported examples of hydrophobicity recovery in these types of hybrid materials after corona treatment. Slow positron beam studies highlighted the formation of a thin silica like layer on the surface of the films after corona similar to that observed for pure cross-linked PDMS compounds. The positron studies enabled estimation of the thickness of the silica like layer.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This study involves the fractionation and characterisation of three propyleneethylene random copolymers. The fractionation technique used in the study was temperature rising elution fractionation (TREF). The TREF fractions were subsequently analysed offline by crystallisation analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC), 13C NMR, high-temperature gel-permeation chromatography (HT-GPC), and wide-angle x-ray diffraction (WAXD). The effect of the ethylene comonomer on the crystallisability of the propylene was investigated, along with the effect of the comonomer on the type of crystal phase formed during the crystallisation. The results show that the comonomer inhibits the crystallisation of the copolymer and that as the ethylene content increases, the crystallisation and melting points decrease. It was also shown that the higher the ethylene content, the more of the γ-phase crystal type is formed. The distribution of the comonomer throughout the copolymers was also investigated. The results show that there is an uneven distribution of the comonomer with most of the comonomer accumulating in the amorphous areas, and very little actually being incorporated in the crystalline regions. It was also observed that the fractions eluting at the highest temperatures had considerably higher polydispersities and lower molecular weights than the fractions eluting just before them. The highest temperature fractions also have lower melting and crystallisation temperatures than the preceding fractions. This has been attributed to a nucleation effect by the sand support used during the TREF fractionation.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Complex polymers are defined by their distributive properties with respect to molecular weight, chemical composition, functionality and molecular topology. As a result, polymer properties are very frequently determined not only by one of these entities but by the correlation of two or more distributions. Aliphatic polyesters are industrially implemented in high performance coatings, paints and varnishes. However, it is typically difficult to correlate the resulting properties with the synthesis parameters as these polymers vary in reactivity and application properties. Copolyester synthesis by direct polyesterification is often assumed to produce randomized products due to the mechanisms involved in stepwise polymerization. The formation of cyclic products by intramolecular reactions of hydroxyl (OH) and carboxylic (COOH) functional groups, sidereactions such as transesterification, alcoholysis, and ester-ester interchange allow even further randomization, enabling a highly complex system. Therefore, in addition to molecular weight distribution, polyesters exhibit chemical composition, functionality type as well as branching distributions, classifying them as complex polymeric systems. The different methods of polymer chromatography in combination with sophisticated spectrometry techniques are useful tools for enabling the full description of the molecular heterogeneity of these complex polyesters. The present study entails method development of different modes of chromatography and mass spectrometry along with their combination, to facilitate the analysis of the various distributions of two model polyester systems, phthalic and maleic anhydride, respectively, in combination with propylene glycol. Gradient HPLC analysis enabled an oligomeric separation based on chemical composition of the respective anhydride/propylene glycol samples. Its off-line coupling to MALDITOF MS and ESI-QTOF MS revealed the presence of several distributions of varying endgroup functionality type and molecular weight distributions at different intervals throughout the polymerization. In addition, online gradient HPLC x size exclusion chromatography (2D-LC) was conducted to obtain the dual chemical composition-molecular weight (CCD-MWD) distribution. The combination of the different coupling techniques provided the opportunity to a more in-depth analysis of the structure-property relationships. / AFRIKAANSE OPSOMMING: Komplekse polimere word gedefinieer deur hul verdelings eienskappe ten opsigte van molekulêre massa, chemiese samestelling, funksionaliteit en molekulêre topologie. Gevolglik, word hul eienskappe dikwels bepaal deur nie net een van hierdie entiteite nie, maar ‘n korrelasie van twee of meer verdelings. Alifatiese poliësters word industrieel geϊmplimenteer in hoë werkverrigting bestrykings, verwe en politoere, dog is dit tipies moeilik om die uiteinde eienskappe met die verwante sintese parameters te korrelleer, aangesien die polimere varieer in reaktiviteit en toepassingseienskappe. Ko-poliëster sintese vanaf direkte poliësterivering word dikwels aanvaar om willekeurige produkte op te lewer as gevolg van die meganismes wat betrokke is tydens trapgroei polimerisasie. Die produsering van sikliese produkte weens intra-molekulêre reaksies van hidroksiel(OH) en karboksiel (COOH) verwante funksionele groepe, newereaksies soos transverestering, alkoholise en ester-ester verwisseling, het verdere ewekansigmaking tot gevolg wat ‘n hoog gekomplekseerde sisteem tot gevolg het. Benewens die molekulere massa verdeling, vertoon poliësters dus chemiese samestelling, funksionaliteit tipe so wel as vertakkings verdeling wat hul as komplekse polimeer sisteme klassifiseer. Die verskillende metodes van polimeer chromatografie in kombinasie met gesofistikeerde spektrometriese tegnieke dien as nuttige bronne vir die volledige beskrywing wat betref die molekulêre heterogeniteit van komplekse poliesters. Die huidige studie stel metode ontwikkeling van verskillende modus van chromatografie, massa spektrometrie sowel as hul aaneenvoeging bekend, om die die verskillende verdelings van twee model poliester sisteme, ftaal- en maleϊensuuranhidried onderskeidelik in kombinasie met propileenglikol, suksesvol te analiseer. Gradiënt hoë-druk vloeistof chromatografie (HPLC) analise het ‘n oligomeriese skeiding, gebaseer op die chemiese samestelling van die verskeie anhidried /propileenglikol monsters, opgelewer. Die nie-gekoppelde skakeling met matriks-assisteerdelaser/ desorpsie-ionisasie tyd-van-vlug (MALDI-TOF) en elektron-sproei-ionisasie kwadrupool-tyd-van-vlug (ESI-QTOF) massa spektrometrie het die teenwoordigheid van verskeie verdelings van varieërende endgroep funksionaliteit tipe en molekulêre verdelings by verskillende intervalle tydens die polimerisasie aan die lig gebring. Gekoppelde skakeling van gradient HPLC en grootte uitsluitings chromatografie is ook uitgevoer om die tweedelige chemiese samestelling-molekulere massa verdeling te bepaal. Aaneenvoeging van die verskeie skakelings tegnieke het die geleentheid gebied om ‘n deeglike studie van die struktuureienskappe verhoudinge suksesvol uit te voer.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A comparative study of the chemical composition of linear low density polyethylene polymers, synthesised with 1 - hexene as comonomer was conducted. Catalyst trials were conducted on the linear low density 1 - hexene polymer grade material to evaluate alternative catalysts. A comparative analysis was performed in order to investigate if the samples synthesised under catalyst trial conditions showed any significant differences in terms of crystallinity and mechanical properties with the reference sample that was synthesised using the reference catalyst. The results showed that the macro product properties, namely melt flow Index, density, and level of hexene extractables are different for the trial samples in comparison with the reference sample. The differences observed implied that the trial samples were synthesised with differences on a molecular level. The differences in the chemical composition between the reference sample and the comparative samples were fully explored using a wide range of analytical techniques, namely crystallisation analysis by fractionation (CRYSTAF), temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), Carbon 13 nuclear magnetic resonance (13C NMR), Size exclusion chromatography (SEC), Positron analysis lifetime spectroscopy (PALS) and micro hardness analysis. The results of the characterisation studies indicated the following: - Crystallinity and hardness analysis of the reference sample, catalyst trial sample 1 and catalyst trial sample 2 indicate that the catalyst trial sample 2 having a low cocatalyst concentration is the most crystalline of all the samples. - The reference sample, catalyst trial sample 1 and catalyst trial sample 2 were further fractionated using TREF at fractionation temperature intervals of 10°C. TREF analysis indicates that the bulk of the material is observed to elute between 70°C - 10°C. - 13C NMR analyses of the TREF fractions identified four populations of fractions that could be selectively removed, allowing the bulk of the material to be recombined. As these highly crystalline fractions were removed, there was an observed decrease in the total crystallinity of the bulk recombined material. This trend was further verified by the free volume analysis. - Free volume analysis indicated of the bulk recombined material indicated a general increase in the T3 lifetime and T4 lifetime intervals. Free volume analysis further confirmed a decrease in crystallinity of the bulk recombined material as highly crystalline material was removed. - Micro hardness analysis of the polymers further verified the crystallinity trends observed. As the molecular composition of the polymer changed due to removal of highly crystalline fractions, the total mechanical strength of the material indicated by the hardness value decreased. The study showed that by changing the chemical composition of the polymer by removing highly crystalline fractions, there was an observed change in the mechanical properties of the polymer. It can be concluded that the samples synthesised under catalyst trial conditions show significant differences in terms of crystallinity and mechanical properties in comparison with the sample that was synthesised using the standard reference catalyst. / AFRIKAANSE OPSOMMING: ‘n Vergelykende analise studie is onderneem van die chemiese samestellings van lineêre lae digtheid poliëtileen polimere, gesintetiseer met 1-hekseen as ko-monomeer. Alternatiewe kataliste is ge-evavuleer ten opsigte van lineêre lae digtheid 1-hekseen Sasol polimeer graad materiaal. Die vergelykende analise is uitgevoer om die monsters onder katalis proef kondisies te evalueer en te merk of enige beduidende verskille in terme van kristalliniteit en meganiese eienskappe met die verwysings monster voorkom. Die resultate toon dat die makro-produk eienskappe, naamlik smelt vloei indeks, digtheid en vlak van hekseen onttrekking, verskillend is vir die proef monsters in vergelyking met die verwysings monster. Die waargenome verskille impliseer dat die proef monsters op molekulêre vlak verskil. Die verskille in chemiese samestelling tussen die verwysings monster en die vergelykende monsters is ten volle ondersoek deur gebruik te maak van 'n wye verskeidenheid van analitiese tegnieke, naamlik kristallisasie analise fraksionering (CRYSTAF), temperatuur stygende eluering fraksionering (TREF), differensiële skandeer kalorimetrie (DSC), koolstof 13 kernmagnetiese resonansie (13C KMR), gelpermeasie chromatografie (SEC), positron analise leeftyd spektroskopie (PALS) en mikro-hardheid analise. Die resultate van die karakterisering studies het die volgende aangedui:- Kristalliniteit en hardheid analises van die verwysings monster en katalis proef monsters 1 en 2 het getoon dat katalis proef monster 2, wat ‘n lae ko-katalis konsentrasie bevat, die mees kristallyn is. - Die verwysings monster en katalis proef monster 1 en 2 is gefraksioneer met behulp van ‘n TREF met temperatuur tussenposes van 10°C. TREF analise toon dat oormaat materiaal ge-elueer word tussen 70°C en 100°C. - 13C KMR analise van die TREF fraksies het 4 verskillende fraksies geidentifiseer wat selektief verwyder kan word. Dit laat ook toe dat die grootste deel van die materiaal weer geherkombineer kan word. Soos die hoogs kristallyne fraksies verwyder is, is ‘n afname in die totale kristalliniteit van die geherkombineerde materiaal waargeneem. Hierdie tendens is bevestig deur vrye volume analises. - Vrye volume analises van die geherkombineerde materiaal toon ‘n algemene toename in die T3en T4 leeftyd aan. Vrye volume analises toon verder dat ‘n afname in die kristalliniteit van die geherkombineerde materiaal plaasvind soos meer kristallyne fraksies verwyder word. - Verdere mikro-hardheid analises van die polimere bevestig die waargenome kristalliniteit tendense. Soos die molekulêre samestelling van die polimere verander as gevolg van die verwydering van die hoogs kristallyne fraksies, so neem die totale meganiese sterkte van die materiaal af; soos aangedui deur die afname in hardheid waarde. Die studie toon dat die verandering van die chemiese samestelling van die polimeer, deur die verwydering van hoogs kristallyne fraksies, 'n waargenome verandering in die meganiese eienskappe van die polimeer laat plaasvind. Daar kan afgelei word dat die monsters, vervaardig onder die katalis proef voorwaardes, beduidende verskille toon in terme van kristalliniteit en meganiese eienskappe in vergelyking met die monster vervaardig deur die huidige verwysings katalis.

For polymers near the glass transition, the dynamics in some regions can be orders of magnitude different compared with the dynamics in other regions only a few nanometers away, so called spatial heterogeneity [1]. In this thesis, single molecule fluorescence microscopy as a powerful tool, was applied to study the spatially heterogeneous dynamics, both orientational and translational, within the polymer matrix near the glass transition temperature. With our total internal reflection fluorescence microscopy (TIRFM) methods, many individual fluorescent dye molecules embedded in the poly (isopropyl acrylate) (PIPA) thin films can be simultaneously excited. Their emission patterns are analyzed using our orientation determination methods [2] to give the true 3D orientational trajectories of the individual molecules. At Tg < T < 1.2 Tg, single molecule tracking was used to study the dye molecules translational diffusion. Results show that, below 1.1 Tg, the probe molecules are in the confined flow region [3]; at T > 1.1 Tg, the diffusion follows normal diffusion model; at T = 1.2 Tg, although the statistical results shows that normal random walk behavior is followed, the individual molecules still show different diffusion behaviors, clear evidence of the spatial heterogeneity that still exists at this temperature. The second part of this thesis is a development of the 3-detector method to determine the 3D orientation of single molecules [4]. This method is based on the work proposed by Fourkas [4] in 2001. Results utilizing this experimental setup are compared with our emission pattern fitting methods. The results show that, with a little bit higher error range (10º in θ, 20º in φ), the 3-detector method can give agreeable orientation fittings, further more, with higher time resolution of < 10 ms. This 3-detector method is useful and can be applied to study the fast orientation dynamics in different systems.

The polymer-like organic material in the Orgueil (Cl) chondrite was analyzed by high vacuum pyrolysis/gas chromatography/mass spectrometry, a new technique specially developed for this type of polymer analysis. Orgueil powder, previously solvent-extracted to remove all soluble organic compounds, whether indigenous or contaminant, was pyrolyzed in temperature steps at 150°, 300°, 450°, and 600°C. Gas chromatographic/mass spectrometric analysis of the vacuum pyrolyzates revealed a series of alkenes to C₈, an extensive series of alkylbenzene isomers, thiophene, alkylthiophenes, and benzothiophene, and the nitrogen compounds acetonitrile, acrylonitrile, and benzonitrile. Comparison of the Orgueil polymer fragments with those reported in polymer analyses of the Murchison and Allende meteorites suggests that qualitatively and quantitatively the Orgueil and Allende polymeric materials are very similar. The presence of acetonitrile, acrylonitrile, and benzonitrile, typical breakdown products of amino acids, in Orgueil pyrolyzates suggests the presence of amino acids in an insoluble form in the meteorite polymer matrix. Changes in the distribution of polymer fragments occurred during high vacuum pyrolyses as the temperature was increased stepwise from 150° to 600°C. These changes imply a progressive alteration in the character of the polymeric material toward a condensed aromatic structure through the preferential loss of aliphatic and heteroaromatic portions at lower temperatures. A possible inference is that the polymeric material in Orgueil is a complex mixture of polymerized materials having different thermal stability. Comparison of vacuum pyrolyzates of the Orgueil polymeric material with pyrolyzates of terrestrial kerogen indicates similarities in composition and structure. These similarities suggest the possibility that meteorite polymers may have formed near the surfaces of meteorite parent bodies by low temperature processes similar to those by which terrestrial kerogen is formed.