Electrokinetic and Optical Study of Ordered Polymer Colloids

The electrokinetic measurements demonstrate the necessity of pH control and the potential influence of salt concentration on the ordering phenomena. According to the modified concepts of effective hard sphere model and Kirkwood-Alder transition theory for ordered dispersions, the predicted phase diagram with the input of electrokinetic potential information agrees qualitatively with the literature data. This agreement implies that the order-disorder transition of a monodisperse latex dispersion results from electrostatic repulsive forces and has the same origin as the hard-sphere transition. Reflection spectrophotometry was employed to study the particle concentration and temperature dependence on the ordered structure of deionized monodisperse latices. Based on Bragg’s law, the experimental nearest interparticle distance was determined from the wavelength at the reflection peaks. The results show that the peaks become broader and are moved toward smaller wavelength with rising particle concentration. The experimental nearest interparticle distance (De) agrees reasonably well with the theoretical distance (Dt) calculated on the assumption of a perfect crystal lattice. The order-disorder transition temperature estimated from the attenuation of reflection intensity increased with increasing latex concentration.