Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO₄ nanoparticles were synthesized in the presence of sodium polyacrylate (PAAS) by a simple precipitation method, with BaCl₂ and (NH₄)₂SO₄ as reactants. The different roles performed by PAAS in the synthesis of BaSO₄ nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the as-synthesized BaSO₄ nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl₂ to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO₄ nuclei. During formation of the BaSO₄ nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO₄ seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO₄ nanoparticles.