Alternating intermolecular hydrogen bonding in linear liquid-crystalline complexes

An extensive work for the realization of tilted liquid-crystalline (LC) phases of operational viability and display interest as tuned by the alternating (double) hydrogen bonding in the linear intermolecular complexes is presented. A new family of double-hydrogen-bonded liquid crystals formed between mesogenic p-n-alkoxybenzoic acids (nO.BAs) and nonmesogenic p-n-cyanophenol(CN Phi OH) moieties is synthesized and studied systematically. Formation of H-bonding complex between proton acceptor/donor groups is confirmed through the corresponding IR spectroscopic shift. The phases and transitions exhibited by the H-bonded LC complexes are studied using polarizing thermal microscopy (TM) and differential scanning calorimetry (DSC). The impact of flexible chain length and the core part (both of the parent mesogenic moiety) is studied. The soft covalent bond interaction of H-bonding and its configuration are found to enhance the thermal stability of LC phases toward ambient temperatures with the simultaneous induction of tilted smectic G phase.