Abstract
Cationic phosphonium-containing particles were prepared by two stage soap-free emulsion copolymerization of styrene with tributyl-4-vinylbenzyl phosphonium chloride (VBPC). The effect of interfacial structure on colloidal stability was investigated. Different shell structures were constructed by varying the conversion at which the shot addition of VBPC was performed. The amounts of phosphonium groups introduced onto the particles were almost constant regardless of the shot conversion. Particle size analysis by transmission electron microscopy showed that the final size of shot latexes was about 180 nm when VBPC was added at a conversion of above 80%. The colloidal stability of various phosphonium latexes was evaluated by measuring the absorbance as a function of time for different KCl concentrations. Adding VBPC at higher conversion (>90%) caused a significant decrease in the critical flocculation concentration of the corresponding latexes compared to that of the latexes when VBPC was injected at between 80 and 90% conversion, although these particles had nearly the same particle size and nearly the same amounts of phosphonium groups. These results may reflect differences in the shell structure.
