Premium
Control of the Morphogenesis of Barium Chromate by Using Double‐Hydrophilic Block Copolymers (DHBCs) as Crystal Growth Modifiers
Author(s) -
Yu ShuHong,
Cölfen Helmut,
Antonietti Markus
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020703)8:13<2937::aid-chem2937>3.0.co;2-i
Subject(s) - copolymer , materials science , chemical engineering , nucleation , crystallinity , crystallization , polymer chemistry , polymer , chemistry , composite material , organic chemistry , engineering
A systematic morphosynthesis of barium chromate particles has been performed by using double‐hydrophilic block copolymers (DHBCs), which consist of a hydrophilic solvating block and a hydrophilic binding block, as crystal growth modifiers to direct the controlled precipitation of barium chromate from aqueous solution. Several kinds of DHBCs with different functional groups COOH, PO 3 H 2 , SO 3 H, SH as well as PEG‐poly(aminoamine) block‐dendrimer copolymers were explored for crystallization and morphology control of barium chromate. Well‐defined morphologies of BaCrO 4 particles can be produced, such as more or less dendritic X‐shaped, elongated X‐shaped, or rodlike particles, flower‐like plates, ellipsoids, spheres, nanofiber bundles, nanofibers, and other more complex morphologies. In the presence of the phosphonated copolymer PEG‐ b ‐PMAA‐PO 3 H 2 (degree of phosphonation: 21 %) at pH 5, large conelike bundles of nanofibers ranging from 10 to 20 nm in diameter with lengths up to 150 μm can be produced at room temperature, whereas replacement of the covalently bound phosphonate groups by the ionic salt analogue dopant fails to produce this structure, indicating the importance of the functional polymer block structures. The time‐resolved formation process of the bundles of nanofibres was investigated, showing a remarkable self‐similarity. At temperatures higher than 50 °C, in plastic flasks or when undergoing continuous stirring, only ellipsoids or nearly spherical particles can be obtained. This shows that the fiber formation relies on heterogeneous nucleation and is in agreement with a recently published mechanism where fiber formation is due to the vectorially directed self‐assembly of primary particles. Our results demonstrate that the integration of DHBCs, taking advantage of the experimental conditions such as crystallization sites, temperature, pH, and reactant concentration, will extend the possibilities for controlling the shape, size, and microstructures of the inorganic crystals by means of a simple mineralization process.