No abstract

No abstract

No abstract

A series of polyethers have been synthesized from 1-(4-hydroxy-4'-biphenyl)-2-(4-hydroxyphenyl)propane and ct, o~-dibromoalkanes having different numbers of methylene units [TPPs]. Both odd-and even-numbered TPPs [TPP(n=odd)s and TPP(n=even)s) exhibit multiple transitions during cooling and heating and they show little supercooling dependence, indicating close-to-equilibrium nature of these transitions. Combining the structural characterization obtained via wide angle X-ray diffraction powder and fiber patterns at different temperatures and the morphological observations from mieroseopy techniques, not only the nematie liquid crystalline phase but also highly ordered smeetic F, smectic crystal 0 and H phases have been identified. The phase diagrams for both TPP(n=odd)s and TPP(n=even)s have been constructed [1][2][3]. Thermodynamic properties (enthalpy and entropy changes) during these transitions are studied based on differential scanning calorimetry experiments. The contributions of the mesogenie groups and methylene units to eaeh ordering process can be separated and they indicate the charaeteristies of these processes thereby providing estimations of the transition types.