Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: See full text for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / The primary focus of the research was the use of adamantane-containing molecules in polymer science. The research is divided into 2 parts, the first involving the syntheses of a new ligand for use in a metallocene catalyst system. The second part involved the synthesis of new monomers for the use in free radical polymerization systems, In the first part of the research, the synthesis of the ligand, 2-dimethyladamantylethylcyclopentadiene was attempted. This was done via the starting materials adamantylethylbromide and dimethylfulvene. In the first step the adamantylethylbromide was prepared via the tosylation reaction of admantaneethanol. Further, the use of either a Grignard or Barbier reaction to insert the 6,6 dimethylfulvene to yield the final product was attempted. The isolation of the final product could not successfully be completed, even though spectroscopic evidence suggested that the synthesis had been partially succssful. In the second part of the reasearch, the monomers 4-(1-adamantyl)phenolmethacrylate, adamantylmethylacrylate and admantylethylacrylate were synthesized. These monomers were homo-and copolymerized using a controlled radical reaction mechanism (RAFT).

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)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Polymeric nanofibrous membranes that act as surfaces offer two compelling properties; they have extremely large surface areas that can be modified and they can offer multiple reactive sites depending on which polymer they were electrospun from. Combining nanofibrous surfaces such as these with photochromic dyes can give remarkable, light responsive materials. In this study, a terpolymer was electrospun and crosslinked (to impart insolubility to the material) to produce a nanofibrous mat that contained surface secondary-hydroxyl units and benzyl chloride units, from which monomers could grow using surface-initiated atom transfer polymerization (SI-ATRP). The surface was further fluorinated though the secondary-hydroxyl moieties to produce a hydrophobic crosslinked nanofibrous surface. n-Butyl acrylate and a photochromic spiropyran dye were copolymerized from the surface using SIATRP, in order to produce a surface that exhibited reversible adhesion towards a water droplet using ultraviolet and visible light as a stimulus to change between the two states. This in principle would allow the droplet to roll off and stick to the surface respectively. Although the surface displayed a colour change when switched, proving that the SI-ATRP had taken place, the droplet of water remained attached to the surface in both states. / AFRIKAANSE OPSOMMING: Polimeriese nanovesel membrane wat dien as oppervlaktes bied twee aantreklike eienskappe; hulle het baie groot oppervlakareas wat gemodifiseer kan word en hulle bied veelvuldige reaktiewe punte, afhangende van die polimeer waarvan hulle ge-elektrospin is. Deur sulke nanovesel oppervlaktes met fotochromiese kleurstowwe te kombineer, kan uitstekende lig reagerende materiale verkry word. In hierdie studie is ‘n terpolimeer ge-elektrospin en daarna gekruisbind (om die materiaal onoplosbaar te maak) om ‘n nanovesel web te kry wat oppervlak sekondêre-hidroksiel en benzielchloried eenhede bevat. Monomere kan dan vanaf hierdie eenhede groei deur middel van oppervlak-geïnisieerde atoomoordrag polimerisasie (OI-AOPR). Die oppervlak was verder gefluorineer via die sekondêre-hidroksiel eenhede om ‘n hidrofobiese, gekruisbinde nanovesel oppervlak te vorm. n-Butielakrilaat en ‘n fotochromiese spiropiraan kleurstof is gekopolimeriseer vanaf die oppervlak deur middel van OI-AORP om sodoende ‘n oppervlak te skep wat omkeerbare adhesie van ‘n water druppel gee as ultraviolet en sigbare lig as stimulus gebruik word om tussen die twee toestande te wissel. In beginsel sal die water druppel vanaf die oppervlak kan afrol én daaraan vassit, afhangende van die toestand van die oppervlak. Alhoewel die oppervlak van kleur verander het met die wisseling tussen die twee toestande, wat as bewys dien dat OI-AORP wel plaasgevind het, het die druppel water bly vassit aan die oppervlak in beide toestande.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: In reverse iodine transfer polymerisation (RITP), chain transfer agents (CTAs) are generated in situ from the reaction between 2,2’-azobis(isobutyronitrile) (AIBN) and molecular iodine. This stage of RITP is the inhibition period, which ends when all iodine has been consumed. The evolution of CTAs was studied for the polymerisation reactions of n-butyl acrylate and styrene respectively. RITP of n-butyl acrylate was performed at 70 °C. In situ 1H nuclear magnetic resonance (NMR) experiments were carried out to study the evolution of CTAs during the inhibition period of n-butyl acrylate polymerisation and the structures A-I and A-Mn-I (where A represents the moiety originating from AIBN, M represents the monomer unit and n is the mean number degree of polymerisation) were observed. A polymer with the general structure A-Mm-I is formed. The molecular weight of poly(n-butyl acrylate) (PnBA) was evaluated with size exclusion chromatography (SEC) and NMR. Structural analysis of PnBA was done using NMR spectroscopy and matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) mass spectrometry. Similar conditions to those used for n-butyl acrylate polymerisation were used for RITP of styrene. The evolution of CTAs during the inhibition period of styrene polymerisation was studied using in situ 1H NMR. The inhibition period of styrene polymerised by RITP was much shorter than expected. This is due the consumption of iodine in the reaction between styrene and iodine which reversibly forms 1,2-diiodo-ethyl benzene. The CTAs A-I and A-Mn-I are formed, as well as 1-phenylethyl iodide (1-PEI). The molecular weight of polystyrene (PS) was determined using SEC and NMR and the functionality was evaluated using 1H NMR. The structure of PS was confirmed with 1H NMR and MALDI-ToF mass spectrometry. By increasing the temperature of the reaction, the inhibition period can be shortened. Both polymerisation systems retain control over molecular weight with an increase in temperature, however, n-butyl acrylate is limited due to the possible formation of mid-chain radicals. The formation of an A–Mm–A population (direct combination of the initiator and styrene) in RITP of styrene results in more initiator being consumed than for n-butyl acrylate, despite limited conversion of styrene to polymer. / AFRIKAANSE OPSOMMING: In omgekeerde-jodium-oordrag polimerisasie, is die kettingoordragagente gegenereer in situ van die reaksie tussen 2,2’-azobis(isobutironitriel) (AIBN) en molekulêre jodium. Hierdie fase van RITP is die inhibisie tydperk wat eindig wanneer alle jodium verbruik is. Die evolusie van kettingoordragagente is vir die polimerisasiereaksies van butielakrilaat en stireen onderskeidelik bestudeer. Omgekeerde-jodium-oordrag polimerisasie van butielakrilaat was uitgevoer by 70 °C. In situ 1H kernmagnetieseresonans (KMR) eksperimente is uitgevoer om die evolusie van die kettingoordragagente te bestudeer tydens die inhibisie van butielakrilaat polymerisasie en die strukture A-I en A-Mn-I (waar A die gedeelte voorstel wat afkomstig is van AIBN, M die monomeer-eenheid en n die gemiddelde aantal polymerisasiegraad verteenwoordig) is ge-identifiseer. 'n Polimeer met die algemene struktuur A-Mm-I is gevorm. Die molekulêre gewig van poli(butielakrilaat) (PnBA) was geëvalueer deur grootte-uitsluitings chromatografie en KMR spektroskopie. Strukturele ontleding van PnBA is gedoen deur die KMR spektroskopie en matriks ge-assisteerde laser desorpsie/ionisasie tyd-van-vlug massaspektroskopie. Soortgelyke kondisies as dié wat gebruik word vir butielakrilaat polymerisasie, is gebruik vir omgekeerde-jodium-oordrag polimerisasie van stireen. Die evolusie van die ketting oordrag agente gedurende die inhibisie periode van stireen polymerisasie is deur in situ 1H KMR bestudeer en die inhibisie periode is baie korter as verwag. Dit is as gevolg van die opname van jodium in die reaksie tussen stireen en jodium wat omkeerbare stireen-di-jodied tot gevolg hê. Die ketting oordrag agente A-I en A-Mn-I is gevorm, sowel as 1-feniel-etiel jodied. Die molekulêre massa van polistireen (PS) is bepaal met behulp van grootte-uitsluitings chromatografie en KMR spektroskopie en die funksioneering is geëvalueer met behulp van 1H KMR. Die struktuur van PS is bevestig deur 1H KMR en matriks ge-assisteerde laser desorpsie/ionisasie tyd-vanvlug massaspektroskopie. Deur die verhoging van die temperatuur van die reaksie, kan die inhibisie periode verkort word. Beide polimerisasie sisteme behou beheer oor die molekulêre massa met 'n toename in temperatuur, alhoewel butielakrilaat beperk word as gevolg van die moontlike vorming van middel kettingradikale. Die vorming van die A-Mm-A spesie (direkte kombinering van AIBN en stireen) in omgekeerdejodium- oordrag polimerisasie van stireen veroorsaak dat meer AIBN verbruik word as butielakrilaat, ten spyte van die beperkte omskakeling van stireen tot polimeer.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Needle-electrospinning is an uncomplicated and highly versatile nanofiber (fiber diameter of 50 to 500 nm) production technique. Nevertheless the process can only produce 0.01 to 1.0 g/h/m2 of nanofibers, unpractical for large-scale productions. Bubble-electrospinning, in the presence of surfactants, is a novel nanofiber mass-production technique developed at Stellenbosch University.[1] The technique is similar to needle-electrospinning only that the surface area of a bubble surpasses that of a solution droplet, making it possible for multiple jets to form on the bubble surface at high field strengths. Thus far little research has been done on the influence of solution properties on the bubble-electrospinning technique. During electrospinning the solution experiences three competing forces, namely, surface tension (contracting force), charge repulsion (expanding force), and viscosity (resistance to flow). The first aim of this study was to obtain better understanding on the influence of three significant solution properties (viscosity, conductivity and surface tension) on bubble-electrospinning in terms of bubble lifetime, bubble size, average number of jets and the resultant fibers. The solution properties were varied using a range of polymer and surfactant concentrations. A second aim was to obtain better understanding on the comparison of the bubble-electrospinning process between two polymer solutions, namely Polyvinyl alcohol (PVOH) solutions containing sodium lauryl ether sulphate (SLES) surfactant, and Polyacrylonitrile (PAN) solutions containing silicone surfactant. Results indicated that the solution viscosity and conductivity increased with increasing polymer concentrations for both polymer solutions. In addition, both the solution surface tensions were not influenced by polymer concentration. With regards to bubble-electrospinning of PVOH solutions, results indicated that the average number of jets per bubble was influenced by the polymer concentration. Regarding PAN solutions, bubble lifetime and the average number of jets was influenced by polymer concentration. Results indicated that the solution viscosity increased and surface tension decreased with increasing surfactant concentration for both polymer solutions. PVOH solution conductivity increased whilst PAN solution conductivity decreased with increasing surfactant concentrations. With regards to bubble-electrospinning of PVOH solutions, the bubble lifetime and bubble size was significantly influenced by the SLES concentration. Regarding PAN solutions, the silicone surfactant concentration had no significant effect on the bubble-electrospinning process. Overall, PVOH fiber diameters decreased with increasing surfactant concentration. There was no common trend between the bubble-electrospinning of PVOH and PAN solutions in relation to their solution properties. It was concluded that solution viscosity, conductivity and surface tension are not the only significant contributing parameters to the bubble-electrospinning process. / AFRIKAANSE OPSOMMING: Die naald-elektrospinproses is 'n eenvoudige, hoogsaanpasbare tegniek wat gebruik word vir die maak van nanovesels. Nanovesels het tipies 'n deursnee van 50nm tot 500nm. Ongelukkig is dit onprakties vir grootskaalse produksie omdat die uitset daarvan beperk is tot 0.01 tot 1.0 g/h/m2. Die borrel-elektrospinproses, waar elektrospinstrale gespin word vanaf die oppervlak van borrels op die oppervlak van die spinoplossing en waar die borrels gestabiliseer is m.b.v. sepe, is 'n nuwe tegniek wat ontwikkel is by die Universiteit van Stellenbosch. [1]. Die tegniek is soortgelyk aan die naald-elektrospinproses in dié sin dat die elektrospinstraal vorm vanaf 'n gelaaide halfsfeervormige oppervlak in die spinoplossing, maar die aansienlik groter oppervlakarea van die borrel in die borrel-elektrospinproses maak dit moontlik om verskeie elektrospinstrale gelyktydig op die oppervlak van die borrel te onderhou. Dit lei tot baie hoër doeltreffendheid in die saamgroeppering van die strale en gevolglik tot hoër nanoveseluitsette. Tot dusver is daar weinig navorsing aangaande die invloed van oplossingseienskappe op die borrel- elektrospintegniek gedoen. Tydens die elektrospinproses ervaar die oplossing drie kompeterende kragte, naamlik: oppervlakspanning (sametrekkende krag), elektrostatiese afstoting (afstotende krag) en viskositeit (vertragende effek op vloei van die oplossing). Die hoofdoelwit van hierdie navorsing was om 'n beter begrip te kry van die invloed van drie gemete oplossingswaardes, d.w.s. viskositeit, elektriese geleidingsvermoë en oppervlakspanning op die borrel-elektrospinproses. Die impak van hierde waardes is spesifiek geëvalueer in terme van borrellewensduur, borrelgrootte, gemiddelde hoeveelheid elektrospinstrale per borrel en die morfologie van die vesels wat in die proses gevorm is. Die tweede doelwit van die studie was om 'n vergelyking te tref tussen die mees optimale oplossingswaardes in die borrel-elektrospinproses van twee baie uiteenlopende polimeerspinoplossings, naamlik polivinielalkohol (PVOH), met natrium dodesieletersulfaat (SLES) as die borrelstabiliserende seep en poliakrilonitriel (PAN) oplossing, met 'n silikoonseep as die borrelstabiliserende seep. Resultate het getoon dat die viskositeit en elektriese geleidingsvermoë toeneem met toename in polimeerkonsentrasie vir beide PVOH- en PAN-oplossings. Verder is oppervlakspanning in beide gevalle nie beduidend beïnvloed deur die polimeerkonsentrasie nie. In die geval van die borrel-elektrospin van die PVOH-oplossings het resultate daarop gedui dat die gemiddelde aantal elektrospinstrale per borrel moontlik beïnvloed kon word deur die polimeerkonsentrasie. In die geval van borrel-elektrospin van PAN-oplossing is bevind dat polimeerkonsentrasie die borrelleeftyd en die gemiddelde aantal elektrospinstrale per borrel beïnvloed. Resultate het ook getoon dat die viskositeit vermeerder en die oppervlakspanning afneem met toename in die konsentrasie van die sepe in beide die polimeeroplossings. Die PVOH-oplossing se elektriese geleidingsvermoë het vermeerder terwyl dit verminder in die geval van die PAN-oplossings met 'n toename in die seepkonsentrasie. Tydens borrel-elektrospin van die PVOH-oplossings is beide borrelleeftyd en borrelgrootte beduidend beïnvloed deur die SLES konsentrasie. By die borrel-elektrospin van PAN-oplossings het die silikoonseepkonsentrasie nie 'n beduidende invloed gehad op die borrelleeftyd en borrelgrootte nie. Oor die algemeen het die gemiddelde PVOH veseldeursnee afgeneem met toename in seepkonsentrasie. Geen algemene tendens kon waargeneem word tussen die optimale oplossingswaardes vir borrel-elektrospin van die PVOH- en die PAN-oplossings onderskeidelik nie. Die gevolgtrekking is dat die viskositeit, elektriese geleidingsvermoë en oppervlakspanning nie die enigste beduidende waardes is wat bepaal of die borrel-elektrospinproses sal werk vir 'n spesifieke polimeeroplossing nie.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / Please refer to full text to view abstract.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Please refer to full text to view abstract

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / Reversible addition fragmentation chain transfer (RAFT)-mediated polymerization has emerged as a versatile method for preparing polymers with control over molecular weight and polydispersity. Inherent in its mechanism is the retention of the chain transfer agent, the RAFT agent, at the polymer chain ends. Typically RAFT agents are made up of two parts, the so called R (leaving) and Z (thiocarbonyl thio, stabilizing) groups. These are retained as the a-and the w-end groups of the final polymer, respectively. RAFT polymerization offers a ready method for preparing polymers with well defined end functionalities. The a-end functionality can easily be built into the R group. The Z group, however, is thermally unstable and can impart color and smell to the polymer. Hence, two new methods for Z end group removal were introduced. Both methods take advantage of the facile reaction between thiocarbonyl thio compounds and radicals. By matching the functionalities of the R group (a-end group) with that of the end modified w-chain end, both methods offer an easy route to accessing telechelic functional polymers. End functional polymers have many important uses in industry and in the biomedical field. An alcohol functional xanthate RAFT agent was synthesized and successfully used to conduct the RAFT-mediated polymerization of N-vinylpyrrolidone (NVP). Characterization by NMR and MALDI ToF MS confirmed that a-hydroxyl-w-xanthate-functional PVP was easily produced. In the first end group modification method radicals were generated as in atom transfer radical addition (ATRA). A hydroxyl functional a-haloester was used as the ATRA initiator with a Cu catalyst system. The alkyl radical produced by this ATRA initiator then replaced the Z group giving a telechelic hydroxyl functional polymer. NMR analysis showed that the thiocarbonyl thio end group was completely removed. The hydroxyl functionality was quantified by derivatizing with trichloro acetyl isocyanate and subsequent analysis by NMR. MALDI ToF MS analysis, however, was inconclusive. In the second method the thiocarbonyl thio end group was removed by simply heating the polymer with hydrogen peroxide, thereby replacing the Z group with a hydroxyl end group at the w-chain end, giving a telechelic functional polymer. The telechelic hydroxyl functional polymer was subsequently crosslinked with a trifunctional isocyanate to make a PVP hydrogel. This confirmed that the end-modified polymer was indeed telechelic. The swelling kinetics of this hydrogel were determined in water at 37 oC.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study aimed to combine the principles of crystal engineering with the properties of cyclotriphosphazene derivatives to construct supramolecular assemblies in the solid state. The ease with which the chloro substituents on cyclotriphosphazenes can be replaced makes them ideal candidates for this study. The substituents were chosen for their ability to form either hydrogen bonding interactions or halogen bonding interactions in the solid state. The cyclotriphosphazene derivatives were co-crystallised with various small organic molecules with complementary functional groups, as well as with other cyclophosphazene derivatives. The aim was to form co-crystals or solvates with these cyclophosphazene derivatives as co-crystals contain a wealth of information regarding the forces governing the aggregation of molecules in the solid state. Cyclotriphosphazenes, with their array of substituents, could broaden the range of potential interactions governing crystalline assembly. Fifteen cyclotriphosphazene derivatives were synthesised and characterised in this study. The novel crystal structures of two cyclotriphosphazene derivatives have been elucidated by single crystal X-ray diffraction. These are 2,2-bis(4-formylphenoxy)-4,4,6,6-bis[spiro(2',2"-dioxy-1',1"-biphenylyl)]cyclotriphosphazene and hexakis(4-cyano-phenoxy)cyclotriphosphazene. In the course of this study two novel polymorphs of hexakis(4-fluorophenoxy)cyclotri-phosphazene were identified and studied. The novel triclinic form undergoes an irreversible transformation to the previously reported monoclinic phase at high temperatures. The reported monoclinic phase, however, transforms to a monoclinic C phase in a single-crystal to single-crystal fashion. It is also suspected that this phase transformation is in fact reversible on cooling of the crystal to temperatures below -45 °C. One novel co-crystal structure of hexakis(4-pyridyloxy)cyclotriphosphazene with terephthalic acid was identified and characterised. However, analysis of the Cambridge Structural Database indicates that co-crystal formation with cyclophosphazenes is not a commonly occurring phenomenon. This leads to the conclusion that cyclotriphosphazenes can be used in crystal engineering as supramolecular building blocks, but their shape and size tend to inhibit the formation of co-crystals. Therefore co-crystal formers have to be chosen with great care. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die beginsels van kristalingenieurswese te kombineer met die eienskappe van siklotrifosfaseen afgeleides om sodoende supramolekulêre versamelings in die vastetoestand te bou. Die gemak waarmee die chloor substituente op die siklotrifosfaseenring vervang kan word, maak hierdie molekules ideaal vir hierdie studie. Die substituente is gekies op grond van hul potensiaal om waterstofbindings of intermolekulêre halogeenbindings in die vastetoestand te vorm. Ko-kristallisasie eksperimente is met die siklotrifosfaseen afgeleides en verskeie klein organiese molekules met komplementêre funksionele groepe uitgevoer, asook tussen die verskeie siklotrifosfaseen afgeleides met mekaar. Die doel was om mede-kristalle of solvate met hierdie siklotrifosfaseen afgeleides te vorm aangesien mede-kristalle ‘n magdom inligting bevat rakende die kragte wat die versameling van molekules in die vaste fase beheer. Die siklotrifosfaseen afgeleides wat ‘n wye verskeidenheid substituente kan dra, kan hierdeur die moontlike intermolekulêre interaksies wat die versameling in die kristallyne vaste fase beheer verbreed. In hierdie studie is vyftien siklotrifosfaseen afgeleides gesintetiseer en gekarakteriseer. Die voorheen onbekende kristalstrukture van twee siklotrifosfaseen afgeleides is in hierdie studie geïdentifiseer, naamlik 2,2-bis(4-formielfenoksie)-4,4,6,6-bis[spiro(2',2"-dioksie-1',1"-bifeniliel)]siklotrifosfaseen en heksa(4-sianofenoksie)siklotrifosfaseen. Die strukture is bepaal deur enkelkristal X-straaldiffraksie. In die loop van hierdie studie is twee voorheen onbekende polimorfs van heksa(4-fluorofenoksie)siklotrifosfaseen geïdentifiseer en bestudeer. Die nuwe trikliniese vorm ondergaan ‘n onomkeerbare faseverandering na die monokliniese vorm by hoë temperature. Die bekende monokliniese P fase ondergaan egter ‘n verdere faseverandering na ‘n monokliniese C fase. Hierdie geskied as ‘n enkel-kristal na ‘n enkel-kristal faseverandering. Daar word ook gespekuleer dat hierdie spesifieke faseverandering wel omkeerbaar is indien die kristal na -45 °C afgekoel word. Een nuwe mede-kristal tussen heksa(4-pyridieloksie)sikotrifosfaseen en 1,3-dibensoësuur is in hierdie studie geïdentifiseer en gekarakteriseer. ‘n Analise van die Cambridge Strukturele Databasis het egter aangedui dat die vorming van mede-kristalle nie ‘n alledaagse verskynsel is in sikotrifosfaseen afgeleides nie. Dit lei tot die gevolgtrekking dat sikotrifosfaseen molekules wel in kristalingenieurswese gebruik kan word as supramolekulêre boustene, maar dat die vorm en grootte van die molekules die kristallisering van mede-kristalle verhoed. Dus moet die molekules wat saam met die siklotrifosfaseen molekules gekristalliseer wil word, goed deurdink word.