Ionic liquid-crystal precursors (ILCPs) for CuCl platelets: The origin of the exothermic peak in the DSC curves

We have recently reported (Taubert, A.; Steiner, P.; Mantion, A. J. Phys. Chem. B 2005, 109, 15542) that DSC traces of an ionic liquid-crystal precursor for CuCl nanoplatelets exhibit an intense exothermic peak. The current paper presents a detailed investigation into the origin of this exothermic peak. Electron paramagnetic resonance spectroscopy, high-temperature X-ray scattering, and isothermal differential scanning calorimetry show that the Cu(II)-Cu(I) reduction is complete after about 35 min. It is the rate-determining step in the CuCl formation process and is responsible for the exothermic peak. Cu(II) reduction strongly overlaps with the formation of a first generation of CuCl particles. The formation of the large CuCl platelets observed in the SEM (Taubert, A. Angew. Chem., Int. Ed., 2004, 43, 5380) is inhibited by the organic matrix and occurs over the course of about 5 h.