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Geprint op :
14 december 2018
10:50:47

Closed DFG/FOM programme

Number 61.
Title Physics of colloidal dispersions in external fields (CDEF) 
Executive organisational unit BUW
Programme management Prof.dr. A. van Blaaderen
Duration 2002-2015
Cost estimate M€ 2.1 (FOM-part)

Objectives
The major goal is a 'microscopic' understanding ‑ on the basic time and length scales ‑ of colloidal dispersions under external control. In doing so a systematic development of theoreti­cal approaches, new simulation techniques and experiments in non-equilibrium is necessary, which focus on the essential physics of the samples and thereby reveal the principles of the external perturbation.

Background, relevance and implementation
Examples for soft matter systems, which comprise at least one structural length scale in the mesoscopic regime between a micrometer and a nanometer, include quite different classes of materials such as colloidal dispersions, polymers, membranes and biological macromolecules. These systems are 'soft' as they react much more sensitively to mechanical perturbations (such as shear) as compared to pure molecular materials. The research activities in the field of soft matter are interdisciplinary and have exhibited a rapid growth and strong diversification. Therefore, a focus on an important part of the whole soft matter realm of research activity is reasonable and necessary, while at the same time maintaining an open view with respect to the interdisciplinary circumstances and the technical applications. In this DFG/FOM programme we focus on the rich physics of colloidal dispersions, under external control (shear, electric, laser-optical and magnetic fields and confined geometrics). The latter are solutions of mesoscopic solid particles with a stable (i.e. non-fluctuating) core embedded in a molecular fluid solvent. Among the various soft matter systems, colloidal dispersions play a prominent role as they can be both prepared and characterised in a controlled way. The effective interaction between the colloidal particles can be tailored by changing, e.g., the salt concentration in the solvent. Moreover, colloidal suspensions can be regarded as the simplest prototype of soft matter: the length scale separation between the molecular solvent and the mesoscopic particles is unique and complete. Spherical particles without any additional structure on the mesoscopic length scale possess the simplest and highest possible symmetry. This directly implies that a simple theoretical modelling of a single particle without many fitting parameters is possible. Exciting questions concern collective many-body effects induced by cooperation and self-organisation of many particles. A striking advantage of colloidal dispersions lies in the fact that these questions can be studied simultaneously by using three different complementary methods, namely experiment, computer simulation, and theory. This can be demonstrated using three examples where considerable achievements have been made in the past, namely the bulk freezing transition, the kinetic glass transition and the investigation of crystal nucleation rates.

Remarks
The programme concerns the FOM contribution to a joint German/Dutch collaboration in a so‑called 'Transregio-sonderforschungs-bereich' with the same title. Mid-term evaluations were held in the Spring of 2005 and 2009. 
The final evaluation of this programme will consist of a self-evaluation initiated by the programme leader and is foreseen in 2015.

Please find a research highlight that was achieved in 2013 within this FOM programme here.