Thermal–mechanical studies on a heterocyclic polymer (BBB). I. Tensile creep and recovery

Creep and recovery measurements have been used to study the thermal–mechanical properties of polybisbenzimidazobenzophenanthroline-dione (BBB) over the temperature interval 30–500°C (in vacuo). The creep measurements were augmented by x-ray diffraction, isothermal contraction, and solubility measurements. It is found that extensive intermolecular association giving a supramolecular structure with (nearly) planar polymeric repeat units stacked in a “graphite-like” array dominates the properties of BBB, and that this structure is maintained at temperatures as high as 500°C. The principal mode of creep gives rise to fully recoverable Andrade creep for which the strain depends on the cube-root of time.