Physico-chemical characterization of complex colloidal systems
Lingsam Tea, Forschungszentrum Juelich
Where : Amphi Holweck
A colloid consist of a dispersion of small objects (from few nanometers to few micrometers) in a continuous phase. This broad definition include emulsions, suspension, foams, or gels. These systems are widely used in everyday life, for example mayonnaise, tooth paste, chocolate mousse or styling gel. To use these systems in various applications, the physico-chemical characterization is essential to better understand the relation between the chemistry (and the structure) and the macroscopic properties. Once the system characterized, the properties can be fine-tuned (concentration, pH, salt concentration…) to match the requirements of the application.
The chemical structure can be determined by NMR, and the hydrodynamic radius or the radius of gyration can be obtained by dynamic and static light scattering or neutron scattering, depending of the size range. An another important parameter for polymer is the average molar mass which can be measured by light scattering and size exclusion chromatography. The rheological behavior of dilute to concentrated solutions can subsequently be characterized to determine if the system is a liquid, a visco-elastic fluid or a solid. In the case of emulsions or suspensions, destabilization as a function of time can be monitored by macroscopic observation, confocal microscopy and analytical centrifugation (following the turbidity). Chemical modification of the polymer or particle can then be carried to confer or tune needed properties (stimuli responsive, increase viscosity, gelation…).
Characterization of different systems will be presented here. Hyaluronic acid hydrogels and LCST behavior of cellulose derivative will be described, then water-in-water emulsions stabilization and characterization are investigated, finally surface charged alcane-PEO micelles are studied.
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