Control of self-assembly of amphiphilic wedge-shaped mesogens by combined magnetic field and temperature treatment

The report elucidates for the first time a significant effect of strong magnetic field combined with thermal treatment on the texture of thin liquid-crystalline films in a smectic state. The metastable texture generated in magnetic field was arrested by crystallization of mesogens during cooling to room temperature. The effect was demonstrated on a series of wedge-shaped amphiphilic mesogens based on 1,2,3-tris-(dodecyloxy)benzene (TDOB): asymmetric 2,3,4-tris-(dodecyloxy)benzene sulfonic acid (TDOBSH) and it's sodium (TDOBSNa) and pyridine (TDOBSPyr) salts. The thermotropic properties and structure of liquid crystal phases of synthesized compounds were addressed by differential scanning calorimetry, polarized optical microscopy and X-ray diffraction. It was shown that depending on the type of counterion the synthesized 28 mesogens form different supramolecular structures. The largest effect of intense mag-29 netic field was observed for the pyridine salt for which an ordered primitive cubic phase 30 texture was generated upon applying magnetic field normal with respect to the film. In 31 contrast, for the corresponding acid an improvement of gyroid cubic phase orientation 32 was detected under magnetic field oriented along the film. A highly ordered columnar 33 phase of the sodium salt showed a minimal effect of magnetic field.