Poly(acrylic acid)–Poly(ethylene oxide) Comb Polymer Effects on BaTiO3 Nanoparticle Suspension Stability

We have studied the effects of poly(acrylic acid)–poly(ethylene oxide) (PAA–PEO) comb polymers on the stability of aqueous BaTiO3 nanoparticle suspensions over a wide pH range in the presence and absence of monoand divalent salt species. The comb polymer architecture consists of charge-neutral PEO teeth attached at random intervals along an ionizable PAA backbone. Potentiometric titrations, light scattering, and turbidity measurements were conducted on pure PAA and PAA– PEO solutions to assess their degree of ionization, radius of hydration, and stability. Adsorption isotherm and rheological measurements were conducted on BaTiO3 nanoparticle suspensions to determine the effectiveness of both PAA and PAA–PEO dispersants. Our observations indicate that the presence of PEO teeth effectively shield the underlying PAA backbone from ion interactions, e.g., counterion-screening or ion-bridging effects, thereby allowing PAA–PEO dispersants to impart stability to BaTiO3 nanoparticle suspensions over a wide range of pH, ionic strength, and ion valency conditions where pure PAA fails.