Polymeric additives that adsorb or interact with a powder surface can affect the growth of crystals during synthesis and the colloidal stability of suspensions. However the exact mechanisms and energetics of these processes are poorly understood and often applied only on a purely empirical basis. To be able to use a more knowledge based approach it would be desirable to predict what type of molecule will have a specific effect on a specific crystal or powder surface. Using molecular level simulations we can obtain the energies of such adsorption reactions and thus predict the degree of affinity for different surfaces and interfaces. This allows us to predict the morphology of crystals precipitated in presence of additives and the coverage of crystals in solution containing polymers. This is of great importance in many areas of application for crystal growth (e.g. pharmaceuticals) colloidal dispersion (e.g. ceramics) and in cements where dissolution, colloidal dispersion and crystal growth are all involved. We have worked on many systems over the years amongst others, copper oxalate and hydroxyl propyl methyl cellusoe (HPMC) [1,2], cobalt oxalate and polymethylmethacyrlate (PMMA) [2] and more recently growth inhibition of calcium carbonate and morphology control of iron oxides are described in the links.
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| Molecular dynamics Simulation snapshots of polyacrylic acid (PAA, Mw 1000) adsorbing onto a stepped and charged calcite (10-1 4) face at (a) 150 ps, (b) 400 ps and (c) 500 ps (Ca = green, C = blue, O = red). |
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Publications :
[1] Jongen, N. Bowen,P. Lemaître,J. Valmallette and Hofmann,H. “Precipitation of self-organised copper oxalate polycrystalline particles in the presence of Hydoxypropylmethylcellulose (HPMC) : control of morphology” J. Coll. Interf. Sci. 226 189-198 (2000).
[2] P. Bowen, O. Pujol, N. Jongen, J. Lemaître, A. Fink, P. Stadleman and H. Hofmann, “Control of morphology and nanostructure of copper and cobalt oxalates: Effect of complexing ions, polymeric additives and molecular weight” Nanoscale, 2, 2470-2477, 2010. (DOI: 10.1039/C0NR00420K)