title: Synthesis of pH-responsive particles with shape anisotropy.
abstract: Seeded emulsion polymerization is used to produce large quantities of shape anisotropic, amphoteric particles in a size range of about 1 μm. Copolymer dicolloids (CDCs) containing pyridine groups are synthesized by swelling spherical, lightly cross-linked polystyrene seeds with a mixture of styrene and pH-responsive monomer 2-vinyl pyridine followed by secondary polymerization to contrast with their analogue homopolymer dicolloids (HDCs) where the swelling step is carried out with styrene alone. After the particles are coated with a nonionic surfactant to minimize van der Waals attractions, surface potentials and aggregation properties of dilute suspensions are studied as functions of pH and ionic strength. Compared to HDCs, which remain stable at all pH values studied (3 < pH < 9) up to an ionic strength of 5 M, the CDC particles show amphoteric behavior with strong attractions under conditions where dipolar interactions are expected to dominate.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
authors.forename: Tianying
authors.initials: T
authors.lastname: Jiang
authors.forename: Charles F
authors.initials: CF
authors.lastname: Zukoski