title: Formation of BaSO4 fibres with morphological complexity in aqueous polymer solutions.
abstract: BaSO4 fibres with morphological complexity were formed in aqueous solution with polyacrylate and partially monophosphonated poly(ethyleneoxide)-block-poly(methacrylic acid) additives by a simple precipitation reaction. For polyacrylate, formation of the fibrous deposits was strongly dependent on the level of supersaturation (S) and Ba2+:polymer molar ratio (R). At S = 60 to 80, and R = 3 to 14, highly anisotropic crystalline fibres consisting of bundles of BaSO4 nanofilaments were formed after several weeks, although the yield was low. The nanofilaments were also organized into cone-shaped aggregates at S = 80, and at lower R values these formed higher-order structures that consisted of multiple cone-on-cone assemblies with remarkable self-similarity. Increasing the supersaturation produced ovoid or cross-shaped dendritic particles for the range of molar ratios studied. In contrast, BaSO4 crystallisation in the presence of a partially phosphonated block copolymer gave a high yield of BaSO4 fibres up to 100 microm in length, and consisting of co-aligned bundles of 30 nm-diameter defect-free single-crystal nanofilaments with a uniform growth tip. A model for the defect-free growth of BaSO4 nanofilaments in aqueous polymer solutions based on amorphous precursor particles, vectorially directing forces and van der Waals attraction is proposed.
authors.affiliation: Max-Planck-Institute of Colloids and Interfaces, Colloid Chemistry, Potsdam, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Qi
authors.forename: H
authors.initials: H
authors.lastname: Cölfen
authors.forename: M
authors.initials: M
authors.lastname: Antonietti
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: J D
authors.initials: JD
authors.lastname: Hopwood
authors.forename: A J
authors.initials: AJ
authors.lastname: Ashley
authors.forename: S
authors.initials: S
authors.lastname: Mann