Control over Dispersion Efficiency of Nano-Size Zno Particles in Aqueous Medium: Correlation between Dispersant Molecular Weight and Particle Size

Aqueous suspensions of zinc oxide (ZnO) nanoparticles are prepared at 0.5 wt% solid content using polyacrylic acid (PAA) as a dispersant. Average particle sizes of the ZnO powder are 65, 175 and 225 nm and the dispersant molecular weights (MW) are 1.8k, 450k and 3000k g/mol. Particle dispersion and stability of the ZnO nanoparticles in aqueous suspensions are investigated to determine the efficiency of each PAA as a dispersant. It is found that the efficiency of PAAs depends significantly on their MW and size of the ZnO nanoparticles. At relatively low dispersant concentration, the PAA(1.8k) is the most efficient one for all ZnO nanoparticles. When the dispersant concentration and size of the ZnO nanoparticles increase, the PAA(450k) becomes the most efficient one. The PAA(3000k) is the worst dispersant in all conditions. This research provides a fundamental knowledge on relationship between particle size and dispersant MW, which is essential for producing a well-dispersed and highly stable aqueous suspension.