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

TL;DR

This study investigates how minimal structural changes in non-chiral liquid crystal homologs influence their ferroelectric and paraelectric phases, revealing insights for designing materials with stable ferroelectric properties.

Contribution

It demonstrates that a single methylene unit difference significantly affects polarity and ferroelectric behavior in smectic phases of homologous liquid crystals.

Findings

Structural modification alters phase polarity without changing transition temperatures.

Longer homologs can sustain ferroelectric phases in mixtures.

Mixtures can exhibit stable ferroelectric properties over broad temperature ranges.

Abstract

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, identifying 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 phase transition temperatures, particularly the sequence and temperature ranges of smectic and nematic phases. Additionally, 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, facilitating the targeted design of non-chiral compounds with polar phases. Moreover, the properties of the studied mixtures underscore the potential to develop multicomponent LC mixtures with stable ferroelectric properties in a broad temperature range, a feature of considerable significance for practical applications.