Effect of nitrogen-doped few-layer graphite nanofragments on mesomorphic, dielectric, and rheological properties of cholesterol tridecylate

The effect of nitrogen-doped few-layer graphite nanofragments (N-GNF) on the physical properties of cholesteric liquid crystal (cholesterol tridecylate) has been investigated. The introduction of N-GNF (0.02 or 0.005 wt.%) alters the phase behaviour and supramolecular organisation of cholesterol tridecylate. Differential scanning calorimetry reveals a redistribution of enthalpies between polymorphic crystalline transitions and broadening of phase transition peaks, indicating increased structural heterogeneity of the studied dispersions. Dielectric spectroscopy shows a stepwise change in static permittivity near the Cr2-SmA transition, correlating with calorimetric data, and reveals hysteresis in the smectic phase related to the kinetics of dipole orientation of liquid crystal molecules. Rheological studies have shown that the introduction of N-GNF into the liquid crystal matrix causes an expansion of the range of existence of the viscoelastic state for the N* phase and a decrease in shear resistance in the SmA phase for all dispersions. The results highlight the potential of N-doped carbon nanomaterials for targeted control of liquid crystal properties for their application in optoelectronics and sensorics.