Synthesis and 13C CPMAS NMR characterization of novel thiophene-based nematogens

The synthesis and characterization of novel thermotropic liquid crystals based on thiophene are reported. In these molecules, a thiophene ring, 1-4 disubstituted phenyl rings, and ester and azomethine linking units form the core fragment, and an alkoxy unit serves as the terminal group. All compounds exhibited an enantiotropic nematic phase, as confirmed by hot-stage polarizing microscope analysis and differential scanning calorimetry. Isotropic C-13 chemical shift values measured from CPMAS experiments on crystalline solid and nematic phases were compared to the values obtained from the static nernatic phase. These experiments demonstrate the alignment of molecules in the magnetic field. Lower melting and clearing values are observed when two phenyl rings are part of the mesogen, while the addition of a third phenyl ring increases these values.