Short chain copper(II)n-alkanoate liquid crystals

Abstract

Four short chain members of the copper(II) n-alkanoate series Cu(Cn) 2 , from propanoate to hexanoate, have been synthesized, purified and characterized by means of optical microscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR and Raman spectroscopy. The TGA study shows that decomposition starts on heating above 420-470 K (depending on the sample) in a nitrogen atmosphere. In addition, thermal decomposition was investigated by DSC using special high pressure pans and endo-and excthermic processes were found which have not been reported previously. All but one of the compounds melt to a liquid crystal phase, which decomposes before the clearing point. The exception is the propanoate homologue, which decomposes directly from the solid state. Despite this problem of sample decomposition, the identification by optical microscopy of the tetragonal (butanoate) and hexagonal (pentanoate and hexanoate) discotic columnar phases was, for first time, possible by the addition of small amounts of the corresponding acid to the samples. These results are in agreement with the X-ray diffraction study performed using swelled mixtures of these salts with hydrocarbon solvents. Two solid-solid transitions, not previously reported in the literature, were found for the butanoate homologue at 395.9 and 422.9 K with DH~8.27 and 1.37 kJ mol 21 , respectively. The solid and liquid crystalline phases were investigated using variable temperature FTIR spectroscopy.

Thermal decomposition of barium valerate in argon

“…In comparison with the FTIR spectrum of Y-valerate [20] the same absorption bands can be found except for the absence of a low intensity absorption band at 1608 cm -1 and for the presence of a visible split in two absorption bands of the νas(CH3) between 2800 cm -1 and 3000 cm -1 in the present case, as can be found too in the case of Cu-valerate [18].…”

“…It presents all the characteristic absorption bands of a valerate by comparison with published data for related compounds like Yvalerate [20], Dy-valerate [19], Li-valerate [21], Zn-valerate [22] and Cu-valerate [18]. The absence of the νs absorption band for H2O around 3400cm -1 [23] indicates that the Ba-valerate produced by the present technique is anhydrous.…”

“…However, the main evolution stage of CO2 is postponed to higher temperatures, because it is "stored" in the reflections. Inset: FTIR spectrum of the sample with band assignments according to [18] and [19]. BaCO3.…”

Studies on the thermal decomposition of lanthanum(III) valerate and lanthanum(III) caproate in argon

“…1. They contain characteristic absorption bands similar to those observed in Dy-valerate [44], Li-valerate [45], Zn-valerate [46], Cu-valerate [47] as well as Y-valerate [48] for the La-valerate sample, and in Cu-caproate [47] and Y-caproate [49] in the case of the La-caproate sample. The detection of broad absorption bands at 3600-3000 cm À1 as well as around 1640 cm À1 in Fig.…”

Synthesis and thermotropic behavior of side chain polysiloxane bearing triphenylene moiety

“…The results from TOA for the triphenylene (4) correlate very well with the data obtained from the differential scanning calorimetry (DSC). TOA analysis of polymer (6) points that on heating of the layer the Cr-LC transition is observed changing the orientation of molecules [33]. This results in an increase in light intensity passing through the layer (red curve Figure 4a, image 1 and 2) at 58°C.…”