Thiazole–acylated barbitals liquid crystals as emerging functional materials: synthesis and phase characterization

A series of bent‑shaped liquid‑crystalline thiazole– hexahydropyrimidine derivatives bearing azo and alkoxy terminal groups was successfully synthesized and characterized. The homologous series 1,3‑dialkoxy‑5,5‑bis [4‑((2‑(4‑ethoxyphenyl) diazenyl) thiazol‑4‑yl) aminophenyl] hexahydropyrimidine‑2,4,6‑ trione, [VI]ₙ (n = 2, 3, 4, 5, 6, 8), was synthesized and structurally confirmed by FTIR, ¹H‑NMR spectroscopic methods and mass spectrometry (MS). Mesophase behavior was examined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Compounds [VI]3 and [VI]4 exhibited only a nematic phase at 185 and 125 °C, respectively. Whereas [VI]₅ showed both nematic and smectic C (SmC) phases at 125 and 141 °C, respectively. Compounds [VI]₆ and [VI]₈ displayed SmC and smectic A (SmA) phases at 159 and 176 °C, respectively. While [VI]₂ showed no liquid‑crystalline properties. The emergence of mesomorphic properties was governed by the number of methylene units present in the alkoxy side chains.