Electron Density Modulations in Columnar Banana Phases

The structure of columnar phases formed by bent-core mesogens is analyzed. The combination of the X-ray diffraction intensity data and the model predictions for the form factor phases allows for the construction of the electron density maps for these phases. Within the model, the smectic layer fragments are approximated by parallelograms placed in a body-centered crystallographic unit cell, the parallelogram size and orientation with respect to the unit cell sides being the free parameters. Obtained maps show that in the tilted columnar phase, the neighboring molecular blocks with opposite electric polarity are connected either through the walls or continuously by the less-ordered layer fragments. The type of connection between the blocks seems to be determined by the size of the crystallographic unit cell.