Structural studies of tubular discotic liquid crystals

Discotic liquid crystals based on the rigid ring-shaped phenylacetylene macrocycle molecule (PAM) are of great interest due to their potential organization into supramolecular channels. We have used high resolution X-ray diffraction to study the structure of pure and doped PAM and to demonstrate that PAM forms a tubular columnar liquid crystal with an unexpected distortion and doubling of the underlying hexagonal lattice. We have doped PAM with different percentages of silver ions and determined that doping did not change peak positions on the powder diffraction data but significantly altered the intensity of the peaks. This implies that the silver ions were most likely intercalated within the channels formed by the PAM molecules, thus leaving the lattice parameters unaffected. We have also used grazing incidence X-ray diffraction and X-ray reflectivity to study Langmuir films of PAM. PAM adopts an “edge-on” molecular arrangement at the air-water interface. We will discuss the direct observation of the structural reorganization within macromolecular Langmuir films of disc-shaped ionophoric molecules arising from interactions with potassium and cesium ions in the subphase. The columnar order is disrupted by CsCl in the subphase and strongly enhanced by KCl in the subphase, thus effectively tailoring the structural properties of the Langmuir films for potential applications. We have also used X-ray reflectivity (XR) and grazing incidence x-ray diffraction (GID) to study Langmuir films of another macrocyclic ionophore: torand (tributyldodecahydrohexaazakekulene, “TBDK”) molecules. TBDK is a rigid, triangular molecule; it has been investigated as a potential surface-active complexing agent. The system forms a stable monolayer at the air-water interface and exhibits two distinct structural phases at lower and higher pressures

Structural studies of tubular discotic liquid crystals

Discotic liquid crystals based on the rigid ring-shaped phenylacetylene macrocycle molecule (PAM) are of great interest due to their potential organization into supramolecular channels. We have used high resolution X-ray diffraction to study the structure of pure and doped PAM and to demonstrate that PAM forms a tubular columnar liquid crystal with an unexpected distortion and doubling of the underlying hexagonal lattice. We have doped PAM with different percentages of silver ions and determined that doping did not change peak positions on the powder diffraction data but significantly altered the intensity of the peaks. This implies that the silver ions were most likely intercalated within the channels formed by the PAM molecules, thus leaving the lattice parameters unaffected. We have also used grazing incidence X-ray diffraction and X-ray reflectivity to study Langmuir films of PAM. PAM adopts an “edge-on” molecular arrangement at the air-water interface. We will discuss the direct observation of the structural reorganization within macromolecular Langmuir films of disc-shaped ionophoric molecules arising from interactions with potassium and cesium ions in the subphase. The columnar order is disrupted by CsCl in the subphase and strongly enhanced by KCl in the subphase, thus effectively tailoring the structural properties of the Langmuir films for potential applications. We have also used X-ray reflectivity (XR) and grazing incidence x-ray diffraction (GID) to study Langmuir films of another macrocyclic ionophore: torand (tributyldodecahydrohexaazakekulene, “TBDK”) molecules. TBDK is a rigid, triangular molecule; it has been investigated as a potential surface-active complexing agent. The system forms a stable monolayer at the air-water interface and exhibits two distinct structural phases at lower and higher pressures