[DSC and temperature-dependent infrared spectroscopic study of hydrogen-bonded liquid crystal complexes].

The hydrogen-bonded liquid crystalline complexes based on 4', 4-bipyridine and 4-(trans-4-propylcyclohexyl) benzoic acid and trans-4-(trans-4-propylcyclohexyl)cyclohexyl carboxylic acid assigned as PCBA-BPy and PCCA-BPy were prepared and measured by polarized optical microscopy (POM), differential scanning calorimeter (DSC) and temperature-dependent FTIR It was found that PCBA-BPy and PCCA-BPy exhibited both smectic and nematic phase while all of their predecessors showed no smectic phase. The temperature-dependent FTIR studies revealed that the hydrogen bonding in complex PCBA-BPy was very different from that in PCCA-BPy. The wave number of C=O band had an obvious change at the crystal 1-crystal 2 transition but almost didn't change at smectic-nematic and nematic-isotropic transition; while in PCCA-BPy, it showed no sudden changes but shift to 1 709 cm(-1) gradually with the increase in temperature. The results from temperature-dependent FTIR studies also revealed that when the temperature was higher than the clearing point of the complexes, both of the complexes decomposed partially.