The balance between paraelectricity and ferroelectricity in non-chiral smectic homologs†

Non-chiral liquid crystals (LCs) exhibiting ferroelectricity, distinguished by their dynamic responsiveness to external stimuli and high spontaneous polarization, provide renewed impetus for research into this area of soft matter and open novel application possibilities. Consequently, the identification of structural elements within LC compounds that promote ferroelectricity in non-chiral systems is of critical importance. In this work, two homologs of rod-like compounds, with phenyl and ester groups in the rigid core substituted by fluorine atoms, differing by a single methylene unit, were synthesized and comprehensively analyzed using complementary experimental techniques and quantum-mechanical modeling. This systematic study presents the first documented instance in which such a minimal structural modification markedly influences the polarity of smectic phases in two homologs without substantially altering the phase transition temperatures, particularly the sequence and temperature ranges of smectic and nematic phases. Furthermore, the findings reveal that the longer homolog, which exhibits paraelectric phases, demonstrates a pronounced capacity to maintain ferroelectric phases in mixtures. These results provide new insights into the critical structure–property relationships between molecular architecture and ferroelectric characteristics in LCs. Moreover, the properties of the studied mixtures underscore the potential to develop LC mixtures with ferroelectric properties in a broad temperature range, a feature of considerable significance for applications.