Phase transition behaviors of the self-assembled structures of a dihydrazide derivative

Precipitates or xerogels of 1,3-bis[(3,4-dioctyloxy phenyl) hydrazide] phenylene (BP8-C) from ethanol or toluene were demonstrated to show three different aggregate structures depending on different cooling procedure, i.e. cubic phase and two kinds of hexagonal columnar phase (denoted as Colh1 and Colh2). DSC measurement indicated that cubic-Colh1 and Colh1-Colh2 transition showed endothermic behavior while Colh2-Colh1 transition showed exothermic, indicating cubic structure was the most stable. Annealing of the BP8-C/ethanol suspension or the BP8-C/toluene gel caused the gradual structural transitions from either Colh1 to cubic or Colh2 to cubic phase. Higher incubation temperature, longer annealing time, or polar solvent could accelerate the transitions from instability structure to stability ones in the gels.