Hierarchical change of hydrogen bonds in phase transitions of molecular assemblages

A hydrogen-bonded fibrous assemblage was formed from an amphoteric azopyridine carboxylic acid. In this report, we described the thermally induced change of hydrogen bonds among phase transitions of the fibrous assemblage. The fibrous assemblage made from an aqueous solution was composed of head-to-tail N⋯H-O strong hydrogen bonds and C-H⋯O weak hydrogen bonds cross-linked among the supramolecular polymers. The C-H⋯O weak hydrogen bonds in the fibrous assemblage were dissociated at 150 °C on 1st heating. On 1st cooling, C-H⋯O weak hydrogen bonds formed through re-crystallization at 17 °C were weaker than those in the original fibrous assemblage.