Browsing by Author "Hadasha, Waled"
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- ItemInvestigation of the copolymerization of butyl acrylate (BA) with vinyl neononanoate (VeoVA-9)(Stellenbosch : Stellenbosch University, 2006-12) Hadasha, Waled; Sanderson, R. D.; Tonge, M. P.; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.ENGLISH ABSTRACT: This study has the goal of illuminating structure-properties relationships for copolymers of vinyl neononanoate (VeoVa-9) and butyl acrylate (BA). The VeoVa-9/BA copolymers were prepared using solution free radical copolymerization and miniemulsion copolymerization. The free radical copolymerization of VeoVa-9/BA at different feed ratios in benzene at 80°C using 2,2'azobis (2-methylpropionitrile) (AIBN) as initiator was investigated. The tenninal model was used to describe the copolymerization of these monomers and the copolymer composition was detem1ined using I H NMR spectroscopy. The reactivity ratios, estimated using the nonlinear least square method, and the 95% confidence interval giving values of the reactivity ratios, which were 0.042 (±0.014) and 6.95 (-0.53 /+0.65) for the VeoVa-9 and BA respectively. The copolymerization kinetics for the VeoVa-9/BA was investigated by following individual monomer consumption rates by in-situ NMR. The use of this method provides useful information about the individual monomer concentration during the course of reaction. The copolymerization reaction shows a higher tendency for BA to react than the VeoVa-9. The copolymerization of these monomers was also investigated in a heterogeneous system using the miniemulsion technique. In these investigations the effect of surfactant, initiator type and water solubility of the monomer on the batch and semi-batch miniemulsion behaviour was demonstrated. The rate of the miniemulsion polymerization increased with increasing surfactant concentration, while the final particle size of the latex decreased with increasing surfactant concentration in the miniemulsion mixture. Two types of initiators were used, water and oil-soluble initiators (ammonium persulphate (APS) and AIBN respectively). The rate of the batch miniemulsion polymerization showed dependency on the type of initiator used as the monomer conversion increased faster with APS than when using AIBN. The average final particle size was also larger when the AIBN was used than it was when the APS was used. The batch miniemulsion showed an increase in the nucleation (inhibition) period and a slower polymerization rate as the VeoVa-9 concentration increased. The increase in the VeoVa-9 concentration in both batch and semi-batch miniemulsions also led to an increase in the particle size. The obtained copolymers were characterized in terms of their chemical composition via two-dimensional chromatography (2-D), and in tern1s of some of their physical properties using dynamic mechanical analysis (DMA) and contact angle measurement. The 2-D analysis showed that all the BA was incorporated in the copolymer; this result was also confinned by IH NMR. The 2-D analysis also showed that the copolymer composition depends on the monomer addition mode in the semi-batch process. The copolymer glass transition temperature (Tg) value showed an increase as the VeoVa-9 concentration increased and the Tg values of the copolymers ranged between the two homopolymers' Tg values. The hydrophobicity of the copolymers increased as the VeoVa-9 concentration increased as was indicated by contact angle measurements.