Studies on Langmuir monolayer of tricycloquinazoline based disk-shaped liquid crystal molecules

The assembly of disk-shaped molecules on surfaces has drawn considerable attention because of their unique electronic and optical properties. We have studied the monolayer of the amphiphilic tricycloquinazoline (AmTCQ) based disk-shaped molecules at the air–water and air–solid interfaces. The AmTCQ molecules form a stable Langmuir monolayer at the air–water interface. The monolayer exhibits gas phase, low density liquid (L1) phase, and high density liquid (L12) phase. In L1 phase, the molecules prefer face-on conformation with their flexible side-chain being interdigitated with the neighboring molecules. Interestingly, the molecular conformations in L12 phase were found to be both the face-on and edge-on. The structure of the aggregates of the molecules on a surface can be influenced by the intermolecular and molecule–substrate interactions. The deficiency in π-electrons of the AmTCQ molecule may lead to a weak intermolecular interaction. The observation of both the conformations of the molecules in L12 phase can be attributed to the weak intermolecular interaction.

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► Stable Langmuir monolayer of tricycloquinazoline (TCQ) based liquid crystal molecules at air-water interface.
► Face-on conformation in low density liquid (L1) phase.
► Face-on and edge-on conformation in high density liquid (L12) phase.