Morphology, structure and chromatic properties of azobenzene-substituted polydiacetylene supramolelular assemblies

An azobenzene mesogen-substituted polydiacetylene which self-assembles into stacks with bilayered two-dimensional structure is investigated in detail by transmission electron microscopy (TEM) as well as X-ray diffraction (XRD). These stacks with bilayer-structure are found to be organized into highly ordered lamellar crystal structures. The substituted polydiacetylene assemblies form a blue phase at room temperature, however, they undergo a well-known thermochromic transition in response to thermal stimulus. In this work, we establish links between chromatic transitions, molecular organization and the morphology of these assemblies. This thermochromic transition has been subjected to detailed investigation by means of Fourier transform infrared spectroscopy (FTIR), XRD as well as TEM. These results demonstrate that the strong intermolecular interaction (pi-pi tacking) between azobenzene mesogens is essential for complete recovery of chromatic transitions of PDA1 films following thermal stimulation.