Crystallization of inorganic (and organic) matter often proceeds via intermediate stages – rather than by simple nucleation and growth mechanisms. These precursor stages not only comprise crystal modifications that are less stable than the final one (Ostwald’s rule of stages), but also amorphous, hydrated (nano-) particles and emulsion-like precursors have been observed. These precursors tend to aggregate or restructure before being dissolved and entering the next structural stage.
Structural information on all these intermediates – and by which mechanisms they form – is essential for the development of (polymeric) additives to control crystallization processes – either to achieve particles with a certain size distribution, with certain functionalities or “simply” to impede crystallization in water treatment processes such as seawater desalination.
Data on the structural evolution of precipitating CaCO3 and other systems obtained by means of X-ray microscopy and quench cryo-transmission electron microscopy will be presented, emphasizing that the respective particle formation processes do not follow classical nucleation and growth mechanisms.[2,3]
Open questions in crystallization and the mode of action of polymers as controlling agents will be outlined and discussed.
 Horn, D.; Rieger, J. Angew. Chem. Int. Ed. 2001, 40, 4330
 Rieger, J.; Frechen, Th.; Cox, G.; Heckmann, W.; Schmidt, C.; Thieme, T.
Faraday Discussions 2007, 136, 256
 Lee, J.; Saha, A.; Montero Pancera, S.; Kempter, A.; Rieger, J.; Bose, A.; Tripathi, A. Langmuir 2012, 28, 4043
Jens Rieger received his PhD 1989 in Theoretical Physics in Germany. The same year he joined the Polymer Physics Department of BASF where he was involved in many R&D projects in the fields of plastics, coatings and paints, foams, cosmetics, pharma formulations, detergents, etc.
Within BASF he is presently responsible for scouting for new technologies in the field of Advanced Materials & Systems and for the incubation of new technological approaches. These activities are supported by the BASF Advanced Research Initiative at Harvard University.
He is one of two BASF “Research Fellows”.
Jens Rieger is author or co-author of more than 100 scientific publications, contributions to books and patents.
Jens Rieger is Visiting Scientist at Harvard University and Distinguished Guest Professor at the Changchun Institute of Applied Chemistry (Chinese Academy of Sciences)