A density study of the textural transition in the nematic phases of a dimerized system

Density measurements were performed near the smectic C (SmC)-nematic (N1)-nematic (N2)-isotropic (I) phase transitions for HOBA liquid crystal. A discontinuity in the density values at the SmC-N1 and N2-I phase transitions was observed. From a thermodynamic point of view these phase transitions are considered to be first order. An additional small change in the density data was observed in the vicinity of the N1-N2 phase transition. This experimental result confirms the existence of these nematic phases previously reported in the literature. Furthermore, the thermal expansion coefficient (β) was also calculated, exhibiting a large peak at the transition. This behavior can be interpreted as an indication that the transition N1/-N2 is weakly first order.