Formation of Unusual 10-Petal BaSO₄ Structures in the Presence of a Polymeric Additive

In this work, the formation of unusual flowerlike structures with 10-petals composed of BaSO₄ single crystalline platelets is described. The structures are obtained at pH 5 in an aqueous solution in the presence of a double hydrophilic block copolymer poly(ethylene oxide)-block-sulfonated poly(ethylene imine) (PEO-b-PEI-SO₃H) by site-specific polymer adsorption. The exposed faces are identified, the atomar surface structures of these faces are calculated, and preferred faces for polymer adsorption are found. A model for the growth of the unusual 10-petal BaSO₄ structures is presented which is based on the nucleation of primary particles, secondary growth of the petals, and finally layer wise petal overgrowth.