Effect of poly(vinyl alcohol) on the rheological and drying properties of aqueous ceria-based suspensions under various pH conditions

Poly(vinyl alcohol) (PVA), as a polymeric binder, was incorporated into ceria-based suspensions to achieve better coating-relevant properties. The pH-dependent feature of PVA on the particle surface altered the interactions between the PVA-adsorbed ceria particles, significantly affecting the rheological and drying properties of the ceria-PVA suspensions. PVA adsorption on the ceria particles was determined by the PVA conformation, which resulted from the pH-dependent degree of ionization of its non-hydrolyzed acetate groups. This adsorption modified the primary interaction between PVA-adsorbed particles in suspensions, leading to either flocculation or stabilization, as confirmed with hydrodynamic diameter and zeta potential measurements. Suspensions with well-dispersed PVA-adsorbed ceria particles exhibited shear-thinning to Newtonian behavior, with weak thixotropic characteristics, whereas suspensions with flocculated particles displayed shear-thinning and strong thixotropic features. The mobility of the PVA-adsorbed ceria particles in sessile suspension droplets during drying, analyzed using multi-speckle diffusing wave spectroscopy, critically affected the final droplet patterns after drying.