RESUMEN
[This corrects the article DOI: 10.1039/D3RA08569D.].
RESUMEN
Synthesis of new supramolecules with specific properties and realistic applications requires a sound knowledge of the structure-property relationships of the synthesized molecules. Non-covalent interaction like hydrogen bonding is conducive in realizing mesomorphism. The induction of the liquid crystalline character is associated with the strength of hydrogen bonds formed between the interacting components, which are affected by the change of polarity and polarizability of both components upon change in their terminal polar substituents. When the polar substituents are similar in their reactivity, how does the size of the polar substituent influence the mesomorphism? New hydrogen bonded liquid crystals are synthesized with fluorine and chlorine as substituents, and the mesomorphic behaviour is studied with the size of the substituent as a critical parameter. The chemical characterization is carried out by FTIR measurements, the phase characterization by polarizing optical microscopy and the thermal characterization by differential scanning calorimetry. The DFT method utilizing wb97x-D theory along with the cc-pVTZ basis set were used for the calculations. The hybrid functional B3LYP-D3 and Gaussian type basis set 6-31G(d,p) were used for studying the orientation of the molecules. It is observed that the ortho substituents reduce the co-planarity, meta substituents lead to the molecular broadening while para substituents exhibited highest mesomorphism by enhancing longitudinal dipole moment. Fluoro substituted compounds are exhibiting higher mesomorphism while the bulky chloro substituents are helping to better stack the molecules possessing longer chain lengths.
RESUMEN
Two novel series of unsymmetrically substituted 1,2,4-oxadiazole viz., R.Ox.C(*)C n compounds are synthesized and characterized. An optically active, (S)-(+)-methyl 3-hydroxy-2-methylpropionate is used to introduce a chiral center in the molecule. A biphenyl moiety prepared by Suzuki coupling reaction is directly attached to the oxadiazole core at C-5 position. Investigations for the phase behavior revealed that the series with a benzyl group on one end of the oxadiazole core exhibits an 1D orthogonal smectic-A phase while the second series with dodecyl flexible end chain shows orthogonal smectic-A and tilted chiral smectic-C (SmC*) phases over a wide range of temperatures. The smectic-C phase exhibits ferroelectric (FE) polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center.