Abstract
Single relaxation of the order of microseconds was observed in an aqueous suspension of monodisperse polystyrene latex by using the electric field pulse technique with conductivity detection. The electric field intensity dependence of the relaxation amplitude could be interpreted by Onsager's theory for dissociation field effect. The dependence of the relaxation time on electrolyte concentration and pH shows minima. From the static and kinetic results obtained, the relaxation was attributed to the association-dissociation of the proton of the hydrogen sulfate group on the surface of the latex particles. The intrinsic association and dissociation rate constants were determined to be (8 +/- 1) x 10/sup 5/ mol/sup -1/ dm/sup 3/ s/sup -1/ and (9 +/- 5) x 10/sup 4/ s/sup -1/, respectively at 25 /sup 0/C. The former value was well interpreted by Astumian and Schelly's theory for the reduction of association rate constants in heterogeneous systems, and the latter value revealed that the hydrogen sulfate group acts as a weak, solid acid such as TiO/sub 2/, Fe/sub 2/O/sub 3/, and Fe/sub 3/O/sub 4/.
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