Effect of molecular structure on dielectric and electro-optic properties of chiral liquid crystals based on lactic acid derivatives

Abstract

Self-assembling behaviour of a few lactic acid derivatives with several ester linkage groups in the molecular core has been studied. The molecular structure–physical property correlations has been discussed in the light of the temperature dependences of the static permittivity, dielectric anisotropy, spontaneous polarization, response time and torsional bulk viscosity for eight chiral ferroelectric liquid crystalline compounds. Depending on the molecular structure these compounds exhibit the chiral nematic (N*) phase, the paraelectric orthogonal smectic A* (SmA*) phase and the ferroelectric tilted smectic C*(SmC*) phase being thermally stable over relatively broad temperature range. The temperature behaviour of the spontaneous polarization clearly confirms the second order nature of the SmA*-SmC* phase transition and the first order nature of the N*-SmC* phase transition. The effect of temperature and molecular configuration on the polarization and on the dispersion anchoring energy coefficients has been established. The obtained results are discussed in order to contribute to the structure – property relationship for the specific class of soft organic materials which can be used for design of smart multifunctional liquid crystalline mixtures aimed for optoelectronic and photonic applications.