Colloidal and electrokinetic behaviour of poly(methyl methacrylate- co-butyl acrylate) latex particles

Abstract

Poly(methyl methacrylate- co-butyl acrylate) latex particles were synthesized by both seeded and unseeded semicontinuous emulsion copolymerization processes. Particle size and surface charge densities were characterized by TEM and potentiometric and conductimetric titrations, respectively. The electrophoretic mobilities of the latexes were studied at different ionic strength and constant pH and then at constant ionic strength and different pH. An investigation of the effect of surface density on ζ-potential is described. Conversion of mobility values into ζ potentials was accomplished according to the theory of Dukhin-Semenikhin in order to take anomalous surface conductance into account. The dimensionless relaxation factor ( Rel) was calculated for the different surface charge density of the latexes obtained. The colloidal stability of the latex particles after addition of KBr at an appropriate concentration was followed monitoring the optical absorbance changes of the dispersion. The critical coagulation concentration (CCC) was obtained from the intersection points of the straight log W-log C line with the x-axis (stability factor vs. concentration). The stability factors of the synthesized latexes were measured at pH 5, 7 and 9. The results indicate that these latexes are electrostatically stabilized.