Small Angle X-Ray Scattering with Microcrystalline Materials
SAXS is routinely used for the characterization of liquid crystalline phases. If the crystalline domains are large and the sample is very viscous the scattering is not averaged over all orientations. The RotorCell enables measuring such samples.
The scattering curves of liquid samples is usually averaged over all particles and all possible orientations. This averaging is achieved by the fact that many particles are illuminated at the same time and the particles are diffusing.
Liquid crystalline phases are often highly viscous. They do not undergo diffusive Brownian motion but show gel-like behaviour. If the size of the microcrystals is large and only a few crystals fit into the incident beam, no sufficient averaging of all crystal orientations is guaranteed. Only one particular configuration is probed by the SAXS experiment. Rotating the sample cell during the measurement is an efficient way of obtaining the ensemble averaged scattering curve for such samples.
Experimental and Results
Liquid crystalline phases formed by monoglycerides (Dimodan LS) and water were investigated with the new SAXSpace. The shown example contains 15 wt% water and was measured at 40°C.
Without rotation the 2D scattering pattern is not smooth. Random peaks from microcrystals of random orientation are visible. When the sample is rotated during exposure with the RotorCell for the SAXSpace (Fig. 1) all possible crystal orientations are averaged.
Fig. 1 RotorCell for the SAXSpace
The scattering curve now shows well defined Bragg peaks and allows identification of the symmetry and dimensions of the liquid crystalline phase (Fig. 2).
Fig. 2 Scattering curves with and without rotation.