Author:

Keywords:

high resolution adiabatic scanning calorimetry (ASC) liquid crystal phase transitions, Science & Technology, Physical Sciences, Technology, Chemistry, Multidisciplinary, Crystallography, Materials Science, Multidisciplinary, Chemistry, Materials Science, liquid crystals, calorimetry, phase transitions, latent heat, critical behavior, ISOTROPIC CRITICAL-POINT, SMECTIC-A TRANSITION, TWIST-GRAIN-BOUNDARY, BLUE-PHASE, HEAT-CAPACITY, TRICRITICAL BEHAVIOR, OCTYLOXYCYANOBIPHENYL, ANALOGY, 0205 Optical Physics, 0306 Physical Chemistry (incl. Structural), Nanoscience & Nanotechnology, 3403 Macromolecular and materials chemistry, 3406 Physical chemistry

Abstract:

High resolution calorimetric techniques have substantially contributed in characterizing and understanding the delicate thermal behaviour near many phase transitions in liquid crystals. In this paper we describe a high-resolution adiabatic scanning calorimetric technique that has proven to be an important tool to discriminate between first-order and second-order phase transitions in addition to render high-resolution information on fluctuations induced pretransitional specific heat capacity behaviour. The capabilities of adiabatic scanning calorimetry are illustrated with experimental results for the isotropic to nematic and the isotropic to smectic A transitions for a series of alkylcyanobiphenyl compounds. For the nematic to smectic A transition results are presented for pure compounds and mixtures of liquid crystals as well as on the effects of added nonmesogenic solutes and nanoparticles. For chiral molecules results for phase transitions involving blue phases and twist grain boundary phases are considered.