Thermal and pressure stimulated effect on mesogenic 4-(heptyloxy)benzoic acid and gold nano rod composite systems

Abstract

Nano composites of gold nano rod (GNR) with hydrogen-bonded calamitic liquid crystal (LC) compound 4-(Heptyloxy)benzoic acid is prepared for five different concentrations of GNR. Pure LC and its composites are characterized calorimetrically, texturally and spectroscopically. Pressure stimulated effects on thermal parameters like peak transition temperature (Tp), change in enthalpy of transition (ΔH) are studied. Decrease in Tp and ΔH is observed for the low concentration of GNRs, whereas these parameters have increased for composite 1 on application of pressure. Texture study confirms the uniform distribution of nano rods in the LC matrix without any sign of aggregation. Schlieren textures for different meso phases and transition between them have been recorded. A less common six-fold brush pattern is observed in Schlieren texture for one of the composites with strength of defect value S = $\pm \frac{3}{2}$. FTIR study confirms the presence of H-bond between host LC molecules to form dimers in pure and composite systems.