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 Col(h1)and Col(h2)). DSC measurement indicated that cubic-Col(h1)and Col(h1)-Col(h2)transition showed endothermic behavior while Col(h2)-Col(h1)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 Col(h1)to cubic or Col(h2)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.