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Langmuir monolayer of a novel molecule containing dimer of disk shaped moiety, viz., terephtalic acid bis-[6-(3,6,7,10,11-pentahexyloxy-triphenylen-2-yloxyl)-hexyl] ester (tp-dimer), was studied at air-water interface. The monolayer of the tp-dimer at air-water interface exhibited the coexistence of condensed and gas phases at large area per molecule which on compression transformed to a uniform condensed phase at lower area per molecule (1.80 nm2) and then collapsed at 1.67 nm2. The monolayer film transferred by Langmuir–Blodgett technique onto a hydrophilic silicon substrate was studied using an atomic force microscope. The topography image showed the film to be of height of about 1.5 nm corresponding to the edge-on configuration of the triphenylene moieties. We have studied the collapse of monolayer at air-water interface as a function of compression rate and temperature. We find that the collapse pressure increased with increase in the compression rate. The surface pressure of the monolayer is considered as stress and compression as strain. The strain rate is related to the collapse pressure by a power law similar to that found in the dendrimers. Our studies on the effect of temperature on the collapse pressure of tp-dimer monolayer showed that the collapse pressure decreased with increase in temperature. We have considered the Arrhenius temperature dependence of the strain rate and calculated the activation energy for the collapse of monolayer. Our analysis of the relative area loss as a function of time in the collapse region suggests that the monolayer collapses by the formation of nuclei of three-dimensional crystallites. [ABSTRACT FROM AUTHOR]

In this work, two novel triphenylene−ammonium−ammonium−triphenylene diads were synthesised. The effect of the peripheral chain length around triphenylene and the length of the linker connecting triphenylene with an ammonium moiety on the liquid crystalline behaviour was studied. The molecular structures were verified using proton and carbon nuclear magnetic resonance, mass spectrometry and elemental analysis. The liquid crystalline properties of these compounds were determined by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction studies. These triphenylene−ammonium-based gemini dimers with tetrafluoroborate as the counter ion were found to exhibit liquid crystalline behaviour with a hexagonal columnar phase morphology. [ABSTRACT FROM AUTHOR]