KAGAKU KOGAKU RONBUNSHU, Vol.26, No.3, 347-353, 2000
Diffusion of microparticles in surfactant gel
The diffusion of polystyrene latex microparticles dispersed in gels formed from worm-like molecular assemblies of surfactant cetyltrimethylammonium-bromide (CTAB) was studied using dynamic light scattering (DLS). The initial relaxation mode of the field correlation function obtained by DLS corresponds to the localized translational displacement of the microparticle entrapped bq; the gel structure. The frictional coefficient for this localized movement is dominated by the viscosity of the solvent (water), irrespective of CTAB concentration determining the density of cross-links. On the Ether hand, the final relaxation mode was attributed to the net translational displacement of the microparticle in the gel. The diffusion coefficient for this net displacement differs much from the value evaluated from shear viscosity of the gel. The net displacement was visually illustrated as a step-wise displacement whose rate is dominated by an activation energy determining the average time interval of the step-wise motion. The interval is estimated as 0.2 similar to 0.3 s assuming that the step-length corresponds to the gel mesh size obtained as the correlation length of the CTAB gel free from the microparticles.
Keywords:CETYLTRIMETHYLAMMONIUM BROMIDE;VISCOELASTIC PROPERTIES;DETERGENT MOLECULES;MICELLE FORMATION;AQUEOUS-MEDIA;LIGHT-SCATTERING