Regensburg 2016 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 10: Colloids and Complex Fluids III (Joint Session CPP/DY/BP)
BP 10.7: Vortrag
Montag, 7. März 2016, 16:45–17:00, H42
Hydration and hysteresis of triblock copolymers — •Bernhard Schummer, Stefan Gerth, and Randolf Hanke — Universität Würzburg, Lehrstuhl für Röntgenmikroskopie
Ternary polyether are block ABA copolymers consisting of polyethyleneoxide (PEO) (A) and polypropylenoxide (PPO) (B). They change their hydrophilic or hydrophobic balance dramatically with their temperature and their concentration in water. This change causes a micelleisation. In this case P123 will be used as a copolymer and SAXS will be the method of examination. For micelles an appropriate model is the core-shell model where the shell mostly consists of PEO and the core mainly of PPO. In this model the SLD’s for core and for shell heavily depend on each other. A new parameter κ = ρc − ρ/ρs − ρ is presented to describe the change of the conformation and hydration of the micelle while including the radii of shell and core. Here ρc is the SLD of the core ρs the SLD of the shell and ρ the SLD of the solvent. The new parameter indicates that the SLD of the core decreases and thus dehydrates with increasing temperature. For instancethe SLD’s of the poloxamer L51 show a similar dependency as P123. The heating and cooling curves of the sample for different small concentrations will be presented and show a hysteresis in the form phase diagram. This can be observed in a diagram where κ is ploted against the temperature. At higher concentrations poloxamers form a liquid crystal. It has already been shown that there is a hysteresis in the cell parameter at high concentrations. This effect can now be attributed to a single component of the system, the form change of the micelle.