Characterisation and synthesis of structured latex particles prepared by emulsion polymerisation
The project involved the synthesis, and subsequent characterisation of structured latex particles, namely materials of core- shell morphology, produced by emulsion polymerisation techniques. The polymeric cores were polystyrene which has a high glass transition temperature, and the outer shell was prepared from a copolymer of vinyl acetate and nbutyl acrylate which has a low glass transition temperature. Five polystyrene core latices were prepared, in which the amount of the crosslinker agent, tetraethylene glycol dimethacrylate, used varied from zero to fifteen mole percent. Experimental work was undertaken in order to evaluate what the effect of varying the crosslink density had on the morphology of the structured latex particles. All of the materials were found to film-form at room temperature, but the particle morphology varied as the crosslinking agent concentration increased. The particle morphology was also dependent on the mode of polymerisation. In general, as the degree of crosslinking increased within the polystyrene cores, the glass transition temperature of this component was raised. At very high levels of crosslinking the particle morphology was found to be less like the idealised core-shell morphology. Overall, raising the crosslink density within the cores led to an increase in mixing of the two components within the particles. Analytical characterisation techniques employed in this project have included dynamic mechanical thermal analysis, differential scanning calorimetry, modulated-temperature differential scanning calorimetry, formation microscopy thermogravimetric analysis, minimum film temperature, transmission electron microscopy and particle sizing using correlation spectroscopy.