Controlled structure copolymers for the dispersion of high-performance ceramics in aqueous media

Abstract

Statistical copolymers of a methoxy oligo(ethylene glycol) methacrylate (OEGMA) and either. 2-(dimethylamino)ethyl methacrylate (DMA) or methacrylic acid (MAA) have been examined as dispersants for barium titanate powder in water and water-isopropyl alcohol mixtures. The dispersing efficiency of the polymers was assessed using gravitational sedimentation and by measuring the particle size distributions of the dispersed powders by disk centrifuge photosedimentometry (DCP). OEGMA copolymers with MAA were very efficient, causing the mean particle size of the dispersed powder to decrease by an order of magnitude in the presence of dispersant. In contrast, OEGMA-DMA copolymers were completely ineffective. The best MAA copolymers gave higher dispersion efficiency over a wider pH range (pH 1 to 10) compared to a typical commercial dispersant Darvan-C, which was efficient only above pH 7. X-Ray photoelectron spectroscopy, zeta potential measurements, infra red spectroscopy and DCP studies all show that the acid-containing copolymers bind strongly to the barium titanate surface via the carboxylic acid groups resulting in good quality dispersions. There were no changes in the dispersion quality due to desorption of the dispersant even after extensive washing and drying of the copolymer-coated particles. The dried particles showed complete redispersion in water even after washing and drying, again indicating strong binding of the copolymer to the oxide surface.