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Novel, high molecular weight poly(dimethylsiloxane) / cycloaliphatic polyester segmented copolymers were prepared and characterized. Specifically, polyesters based on dimethyl 1,4-cyclohexane dicarboxylate and 1,4-butanediol were employed. The copolymers were synthesized via a melt process using a high trans content isomer which afforded semi-crystalline morphologies. Aminopropyl terminated poly(dimethylsiloxane) oligonlers of controlled molecular weight were synthesized and then end capped with excess diester to form a diester terminated amide linked oligomer. The latter was then incorporated into the copolymer via melt transesterification step reaction segmented copolymerization. The molecular weight of the polysiloxane and chemical composition of the copolymer were systematically varied to prepare a series of segmented polyester / poly(dimethylsiloxane) copolymers. / Ph. D.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Unsaturated polyesters resins (UPRs) of maleic anhydride (MA), phthalic anhydride (PA) and propylene glycol (PG) were synthesized using the fusion polycondensation process for use in Multi-vesiculated Particles (MVPs). The UPRs were synthesized using different MA:PA mole ratios and process parameters, including heating rates, agitation speed, exotherm rate and maximum processing temperature. Design of Experiments (DoE) software (Design Expert 7) was employed to find the optimum experimental space, i.e. least amount of experiments, but covering all the factors. The variations in the formulation and process parameters had a significant effect on the molecular structure and physical properties of the UPRs. The molecular structure and physical properties of the UPRs was successfully determined using various techniques including viscometry, acid-base titration, Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy, Size-Exclusion Chromatography (SEC), Fourier Transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Furthermore, the carboxyl and hydroxyl end-group concentrations of the UPRs were determined by derivatization of the groups with trichloroacetyl isocyanate (TAI) and analysis by 1H NMR. As a second part of the study, the effect of the above-mentioned monomer ratio and process factors of the UPRs, on the properties of the MVPs (produced from the UPRs), was investigated. Results showed that these factors had a significant effect on the particle size and degree of vesiculation of the MVPs. The degree of vesiculation of the MVPs was determined by Scanning Electron Microscopy (SEM). Attempts were also made to determine the relative hardness of the MVPs by AFM and microhardness testing to determine a relationship with UPRs properties (e.g. molecular weight, degree of unsaturation and chain branching). These techniques were however found to be unsuitable due to the physical nature of the MVPs. / AFRIKAANSE OPSOMMING: Onversadigde poliësters (OPs) van maleïensuuranhidried (MA), fataalsuuranhidried (PA) en propileen glikol (PD) is berei deur die fusie polikondensasie-proses vir gebruik in multi-vesikulerende partikels (MVPs). Die OPs is berei deur gebruik te maak van verskillende MA:PA molverhoudings en reaksie faktore wat verhittingstempo‟s, roerspoed, eksoterm tempo en maksimum reaksie temperatuur, insluit. As gevolg van die groot hoeveelheid faktore is eksperimentontwerp sagteware (Design Expert 7) gebruik om die aantal eksperimente te verminder, maar ook waardevolle afleidings van die data te maak. Die verskille in die formulasie en reaksie faktore het „n merkwaardige effek op die molekulêre struktuur en fisiese eienskappe van die OPs gehad. Hierdie eienskappe is bepaal m.b.v. verskeie tegnieke, naamlik viskometrie, suur-basis titrasie, Proton Kern-Magnetiese Resonansie (1H KMR) spektroskopie, Grootte-Uitsluitings-Chromatografie (SEC), Fourier Transform Infrarooi (FTIR) spektroskopie en Differensiële Skandeerings Kalorimetrie (DSC). Die hidroksiel en karboksielgroep konsentrasies van die OPs is bepaal deur hul reaksie met trichloroasetiel-isosianaat (TAI) gevolg deur 1H KMR analise. In die tweede deel van hierdie studie is die invloed van bogenoemde faktore op die eienskappe van die MVPs ondersoek. Die resultate het getoon dat hierdie faktore „n merkwaardige effek op die partikel grootte en graad van “vesiculation” van die MVPs gehad het. Die graad van “vesiculation” van die MVPs is bepaal met behulp van Skandeer Elektron Mikroskopie (SEM). Pogings is ook gemaak om die relatiewe hardheid van die MVPs te bepaal deur middel van AFM en Mikro-hardheid toetsing. Dit is gedoen om die verhouding van die OPs eienskappe (molekulêre gewig, graad van onversadigheid en sy-kettings) vas te stel. Hierdie tegnieke is egter ongeskik bevind as gevolg van die inherente fisiese aard van die OPs.

The thesis constitutes investigations from two distinct areas of research. One part deals with controlling and modulating the conformation of linear polymer in solution. Folding of a polymer chain has been achieved by utilising weak non-covalent interactions interaction like metal ion binding, charge-transfer complex formation and solvophobic effect in tandem. The second part of the thesis deals with synthesis and characterization of end-functionalized polymers prepared by melt-transesterification. The thesis is divided into five chapters. Chapter 1 provides a general introduction on foldamers – a class of polymers that adopts an ordered conformation in solution and various approaches to obtain end-functionalized polymers. Chapter 2 describe the attempts to improve the association constant (based on earlier works reported by Ghosh and Ramakrishnan) between the external folding agent and the polymer repeat unit. The polymer used in this study constitutes an electron deficient pyromellitic dimide units (PDI) linked with a flexible oxyethylene glycol spacer. An electron rich dialkoxy naphthalene (DAN) serves as the folding agent which forms a charge-transfer (C-T) complexation with the electron deficient aromatic units (PDI) in the polymer backbone and effects the folding. The folding agent has the metal ion as its integral part and this aids the interaction between electron-deficient and electron-rich aromatic units by complexing with oxyethylene glycol spacer. Thus folding is due to the synergistic effect of C-T complex formation and metal ion binding. Further a new polymer with larger -surface area of electron acceptor units was prepared with naphthalene dimide (NDI) unit instead of PDI unit which is expected to show higher folding propensity. Chapter 3 explores the possibility of modulating the folding of the donor acceptor (D-A) polymer. A D-A polymer consist of adjacently placed DAN and PDI units linked by an oxyethylene glycol spacer. Folding of the D-A polymer is effected in the presence of suitable metal ion that binds to the oxyethyleneglycol spacer. Random copolymers with segments of alternately placed D-A pairs and segments that is devoid of D-A pairs were prepared. Depending on composition of the random copolymer, the stack length was shown to be modulated as evident from UV-visible and NMR titration experiments. Following a similar approach, a two step folding of the synthetic polymer was demonstrated. The synthesis and characterization of end functionalized polyesters by melt transesterification is discussed in chapter 4. Well defined linear polymer with propargyl group as the end functionalizable group is prepared by the polycondensation of AB type monomer whereas polycondensation of AB2 type monomer leads to peripherally functionalized hyperbranched polymer. Azide-alkyne ‘click’ reactions carried out at the chain end of linear polyester with fluorophores allowed the estimation of the molecular weight by UV-visible and fluorescence spectroscopic method which is compared with estimation from 1H-NMR. Similarly the glass-transistion temperature of hyperbranched polyester is modulated by the peripheral functionalization with various organic azides by ‘click’ reaction. Chapter 5 gives the conclusion and future directions based on the findings from the thesis work.