Calorimetric, electrooptic and dielectric studies of phase transitions The subject of the research is mainly chiral and achiral liquid crystalline compounds that show rich phase polymorphism. Molecules of the compounds studied show high shape anisotropy, i.e. they are rod-like. What do typical molecules of liquid crystals look like? Molecule of achiral compound (thioester 10_S5) Molecules of selected chiral compounds Calorimetric studies One of the methods, which allow studying phase transitions occurring in polymorphic samples, is Differential Scanning Calorimetry (DSC). This method gives information about transition temperature as well as enthalpy and entropy changes at transitions. Our laboratory is equipped with the Differential Scanning Calorimeter PERKIN-ELMER Pyris 1 DSC . DSC curves obtained for a chiral compound Textures of achiral liquid crystals Texture is known as a spatial orientation of molecules, which is observed in a thin cell using polarizing microscope. Texture observation giving the transition temperatures are done by using polarizing microscope Jenapol of Carl Zeiss Jena Company and METTLER-TOLEDO F82HT hot stage Texture observation versus temperature allows identifying different phases     Texture of crystalline state, and highly ordered smectic J and smectic B phases   Two different textures of smectic C phase: fan-shaped and Schlieren   Fan-shaped textures of smectic A phase   Two different textures of nematic: thread-like and Schlieren   Nematic – Isotropic phase transition: border line of nematic and isotropic phases and nematic droplets in isotropic phase Chiral compounds Tilted phases (SmC*, SmI*, SmF*) of chiral and polar compounds exhibit ferroelectric properties. Ferroelectric liquid crystalline phase was discovered by R.B. Meyer et al. in 1975 (R. B. Meyer, L. Liebert, L. Strzelecki, P. Keller, J. Phys. (Paris) Lett. 36, L69, 1975). Nowadays there are known ferro-, antiferro- and ferrielectric liquid crystalline phases as well as sub-phases. The subject of our studies is connected with phase transitions as well as physical properties of different phases. Spontaneous polarization measurement using reversal current method Sample response to external triangular voltage   Temperature dependence of spontaneous polarization (PS) Dielectric studies Liquid crystals are dielectrics, which exhibit rich dielectric spectrum. Molecular and collective dynamics is studied by using dielectric relaxation method. As a result of these studies one can obtain the dispersion and absorption curves, known as dielectric spectra. As an example, the dielectric spectra obtained for different processes are presented below. The scatters are experimental data whereas the solid line is a fitted theoretical curve according to Cole-Cole function: where Δε = εo -ε∞ is dielectric increment, τ -relaxation time, α - distribution parameter of relaxation time Two dielectric processes in the antiferroelectric SmCA* phase One relaxation process (Goldstone mode) in the ferroelectric SmC* phase One relaxation process (soft mode) in the paraelectric SmA* phase Temperature dependence of relaxation frequencies ν (ν = 1/2πτ) for different collective processes occurring in smectic phases: antiferroelectric SmCA*, ferroelectric SmC* and paraelectric SmA*.