Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008.
The synthesis of glycopolymers with various comonomers as prepared via the RAFT process is investigated. The macro-RAFT agent poly(3-O-methacryloyl-1,2:5,6-di-O-isopropylidene-D-glucofuranose) (PMAlpGlc) was prepared by polymerization of the glycomonomer with cumyl phenyl dithioacetate as the chain transfer agent. Chain extension with styrene or methyl acrylate or acrylic acid afforded novel diblock copolymers, (PMAlGlc-b-poly[styrene] or PMAGlc-b-poly[methyl acrylate] or PMAlGlc-b-poly[acrylic acid]), with predetermined molecular weights and narrow molecular weight distributions. The poly(acrylic acid) based glycopolymer was used to modify the surface of CaCO3, forming what will be referred to as a ‘sugar-coated CaCO3’ particle. This surface modifying effect was evaluated in depth; a schematic study of the effect of reaction temperature, pH, reaction time and glycopolymer concentration on CaCO3 crystallization was carried out. The analytical techniques Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) were used to verify that these ‘sugar-coated CaCO3’ particles have an increased adherence to cellulose compared to ‘non sugar-coated’ particles. A series of polymer configurations comprising various ratios of glycomoiety to poly(acrylic acid) was prepared. The effect of this polymer series on CaCO3 crystallization was evaluated and the ideal polymer configuration and its optimum synthesis conditions (i.e. reaction pH, temperature, time and polymer concentration) that gave maximum adherence of the ‘sugar-coated CaCO3’ particle onto cellulose were identified. The ability of these poly(acrylic acid) based glycopolymers to increase the interaction between CaCO3 and cellulose was then evaluated. This was done by simply mixing all three substrates, i.e. glycopolymer, cellulose and CaCO3 together. Analysis by TGA, SEM and Thin Layer Chromatography (TLC) revealed both the ideal polymer configuration that favoured increased adherence of the CaCO3 to cellulose and the optimum reaction conditions required for application and testing. In addition to studying the interaction between cellulose and CaCO3, the amphiphilic nature of the glycopolymers was determined. Transmission Electron Microscopy (TEM) confirmed that coreshell particles were prepared and that these particles are solvent exchangeable (in the case of styrene and methyl acrylate glyco-blocks) or pH exchangeable (in the case of acrylic acid glyco-blocks).