Synthesis and thermotropic properties of novel double-chained quaternary ammonium chlorides with symmetric and asymmetric hydrocarbon chain length

A series of novel double-chained quaternary ammonium chlorides with symmetrical and asymmetrical hydrocarbon chain length R1–O–CH2–CH(OH)–CH2–N+(CH3)2–R2·Cl− (R1, R2: C12H25, C14H29, C16H33) have been synthesized by the reaction of 1-O-alkyl glycidyl ether with N,N-dimethylalkylamine and N,N-dimethylalkylamine hydrochloride. Their chemical structures have been characterized through FT-IR, 1H NMR, MS and elementary analysis. Their thermotropic properties have been examined by differential scanning calorimetry (DSC), polarizing light microscopy (PLM) and X-ray diffraction (XRD). It has been found that the compounds with longer hydrocarbon chain length and being higher asymmetry in hydrocarbon chain length exhibit lower melting point (Tm), isotropization temperature (Ti) and narrower mesophase temperature range. However, the hydrocarbon chain length and the symmetry in the hydrocarbon chain length have little influence on the type of liquid crystals. All compounds form cholesteric liquid crystal.