Wide-angle X-ray diffraction (WAXD), polarized optical microscopy, and differential scanning calorimetry (DSC) have been employed to elucidate the mesophase transitions in a thermotropic liquid crystalline polymer (LCP) prepared by copolymerization of Bisphenol E diacetate, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. A single glass transition temperature (T,) and double endotherms were discerned in the DSC scans of the neat LCP. The dual melting peaks, commonly attributed to the fast and slow melting transitions, manifest strong dependence on thermal history. Annealing slightly above the Tg transition temperature has shown the occurrence of a solid-solid crystal transformation. However, annealing in the vicinity of melting temperatures exhibits a loss of positional ordering of solid crystals, then reorganization occurs due to the large anisotropy of rod-like macromolecules. Finally, the terminal melting transition takes place. This kind of order-disorder transition of mesophase structures is similar to the phenomenon of meltingrecrystallization in some flexible chain crystals and will be discussed based on new evidence from isothermal WAXD studies.

Thermochemical looping splitting of water and carbon dioxide (CO2) with greenhouse-gas-free (GHG-free) energy has the potential to help address the Gt-scale GHG emissions challenge. Reaction thermodynamics largely contributes to the...

A thermotropic liquid crystalline copolymer consisting of bisphenol E diacetate, isophthalic acid and 2,6-naphthalene dicarboxylic acid was blended with polyether imide by dissolving in a mixed solvent of phenol/1,1,2,2-tetrachloroethane in a ratio of 60/40 w/w and co-precipitating the ternary solution in non-solvent (methanol). Wide-angle x-ray diffraction and differential scanning calorimetry studies revealed that the blends were completely amorphous with a single glass transition temperature. The single phase was probably entrapped during solvent removal, but these mixes were unstable and phase separated upon heating. Mesophase structure developed in the LCP rich region with continued annealing. The evolution of crystalline texture was monitored by time-resolved wide-angle x-ray diffraction following a temperature jump from ambient to 265 °C. The recrystallization process of LCP was found to slow down in the blend state relative to that of the neat LCP.