Streuexperimente an konzentrierten Dispersionen

In this contribution the ordering and stacking kinetics of layered concentrated colloid dispersions are described, especially the structure in a layer and between the layers. For this purpose the theory of Bragg reflections in the liquid and solid state is applied. The charge stabilised particles of defined site and small polydispersity are prepared by the technique of emulsion copolymerisation. The solid like structures were prepared in a Couette or disc shear cell. The uniform crystal ordering was achieved by shearing. By the method of small angle scattering of X-rays the vectors of scattering were obtained. Rotation of the sample perpendicular to the incident beam yields the intensity distribution along certain Bragg rods in the reciprocal space necessary for studying the stacking order. Two ways of getting structure information on the mentioned dispersions were applied. In the first case using the step by step method the dispersion was rotated perpendicular to the direction of flow (beta-rotation). Secondly the hexagonal layers in the Couette cell were oriented by the self-focusing tangential position parallel to the beam direction. The intensity distribution along the Bragg rods perpendicular to the layers is determined by the scattering. The results of this less accurate tangential method are comparable with those of the more exact step by step procedure. It is a new attractive method of getting information about the structure of concentrated colloidal dispersions. The oriented structure of the colloidal systems can be verified by comparing the results of these two methods with those of radial scattering. Two different aspects of crystallisation are available from the white or black Bragg rods. First the growing of cubic crystals along the black rods was recognised by the determination of the layer distances c. Secondly kinetics of the structure of the random or crystalline stacking of the hexagonal layers is investigated by the homogenous or inhomogenous intensity distribution of the white Bragg rods. In this case the transition of the closed packed fcc crystal to the random stacking sequence or vice versa was observed with spontaneous or forced manipulation of the dispersion ordering due to variation of the inner (range of interaction, particle distance, relaxation time) or outer (shear rate) parameters. By seed emulsion polymerisation it is possible to prepare core shell particles with a shell adopted to the medium, which are necessary for the microscopic investigation or light scattering investigations of concentrated dispersions. Particles with this wanted structure and a small polydispersity were obtained neither in one nor in two polymerisation steps.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Kubetzki, Hedwig

Contributors dc:contributor

• Versmold, Heinrich

• info:eu-repo/classification/ddc/530
• Physik
• konzentrierte Latexdispersionen
• Struktur
• Dynamik
• Kleinwinkelröntgenstreuung
• Couette-Zelle
• tangentiale Methode
• Schritt-für-Schritt-Methode
• Bragg

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121385%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59615