hrvatski

Correlation between geometry and formation of spontaneously chiral twist-bend nematic phase

Since the twist-bend nematic phase (NTB) has been predicted for bent-shaped molecules[1], a series of studies reported the evidence of chiral molecular organization within the NTB phase. This chiral organization is consistent with an oblique helicoidal structure and is obtained even when the molecules are achiral. Despite an effort to determine how variations in molecular structure affect incidence of the NTB phase, a general and comprehensive relationship between molecular structure and the formation of the NTB phase is still elusive [2, 3]. Herein we report a comprehensive study, which includes synthesis, mesomorphic properties and molecular modeling, of novel carbonyl- or ethenyl- linked symmetric dimers (Figure 1.a). This new sets of dimers primary differ in the nature of linkage group. Transition properties for ethenyl-linked dimers show that all compounds display both, the uniaxial nematic and NTB phase. In contrast to ethenyl series, the NTB phase was observed only in the homologues with the shortest terminal chains, regardless to the spacer length. Comparison of mesomorphic properties of these two series complemented with computational studies of conformational space around the linkage group revealed that intramolecular torsion in conjunction with molecular curvature plays important role in formation of a spontaneously chiral twist-bend nematic phase. (Figure 1.b).

liquid crystalline dimers ; NTB phase ; , structure-property correlation

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