The Synthesis and Characterization of Thermotropic Liquid Crystal Model Compounds

Recently, the unique morphological classification of the “liquid crystal” state has simultaneously aroused the interest of the industrial and scientific community. With this renewed interest has come a need for better understanding and characterization of the liquid crystal transitions which occur within the many polymeric systems exhibiting this morphological phenomenon. Of the seven newly synthesized thermotropic materials for this study which are p-hydroxybenzoic acid modified compounds, six were of the rod-like geometry typically associated with mesogens. The seventh compound, a derivative of pentaerythritol, was cross-shaped and had a crystalline morphology. All compounds, including the p-hydroxybenzoic acid modified mesogenic precursor, were subjected to various characterization techniques such as proton Nuclear Magnetic Resonance (NMR), infrared spectroscopy (IR), and elemental analysis for structure determination, as well as differential scanning calorimetry (DSC), polarising microscopy equipped with a hot stage, and Fischer-Johns apparatus for thermal analysis.

Results of this study reconfirms previous investigations of similar low molecular oligomers with mesogenic forming ability both in terms of the predictable and of the actual range of the thermotropic and thermodynamic transitions. A different morphological state exists for at least two of the compounds which seemed to exhibit both crystalline and liquid crystalline states. The existence of this morphology created the opportunity for comparison of model compounds of this study with that of polyurethanes.     

Alo?reactionen

Ohne Zusammenfassung     

Chinaalkaloide

Ohne Zusammenfassung     

Untersuchung des Mehles

Ohne Zusammenfassung     

Cacao und Chocolade

Ohne Zusammenfassung     

Structure studies of neutron-rich beryllium and carbon isotopes

The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion induced transfer reactions. A strong sensitivity to the chosen core nucleus is found for the cores of ⁹Be and ¹⁰Be, respectively. With a ⁹Be core, molecular rotational bands up to high excitation energies are observed due to the pronounced 2α-cluster structure, whereas only few states at low excitation energies are populated with a ¹⁰Be core. For ¹¹Be a detailed investigation has been performed for the three states at 3.41 MeV, 3.89 MeV and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2⁺, 5/2^? and 3/2^?, respectively. Furthermore we have studied particlehole states of ¹⁶C using the ¹³C(¹²C,⁹C)¹⁶C reaction and found 14 previously unknown states.