Article,
Synthesis of controlled-structure sulfate-based copolymers via atom transfer radical polymerisation and their use as crystal habit modifiers for BaSO4
J. Mater. Chem., 12 (4): 890 -- 896 (2002)
Abstract
Atom Transfer Radical Polymerisation (ATRP) has been used to polymerise
ammonium 2-sulfatoethyl methacrylate (SEM) in aqueous media using
various poly( ethylene glycol) (PEG) macro-initiators to give a range
of controlled-structure, sulfate-based block copolymers. Such PEG-SEM
diblock copolymers are effective crystal habit modifiers for the
in situ precipitation of BaSO4 in dilute aqueous solution. In the
presence of the PEG-SEM copolymer, near-monodisperse, lozenge-shaped
BaSO4 particles were obtained, depending on the relative block lengths.
X-Ray diffraction and thermogravimetric analysis of these particles
demonstrated that they are polycrystalline in nature and contain
around 8% copolymer by mass. This compares with the characteristic
polydisperse rectangular platelets of single crystal BaSO4 obtained
in the absence of the copolymer. Control experiments suggest that,
while only the SEM block interacts directly with the particle surface,
the PEG block also plays an important role in controlling the crystal
growth. Independent variation of the PEG and SEM block lengths therefore
provides a subtle mechanism for controlling the morphology, size
distribution and crystalline structure of the inorganic phase.
