Intertwined lamello-columnar coassemblies in liquid-crystalline side-chain π-conjugated polymers: Toward a new class of nanostructured supramolecular organic semiconductors

A set of liquid-crystalline polymeric systems, associating at once the regioregular polythiophene backbone and pending mesogenic triphenylenes, is reported. Two series, namely regular homopolymers and alternating copolymers, were prepared by adapting a Grignard metathesis-based methodology, allowing some of the relevant structural parameters to be sequentially and independently modified. The thermal and self-organization behaviors of these uncommon macromolecular systems were investigated by polarized-light optical microscopy, differential scanning calorimetry and temperature-dependent small-angle X-ray scattering. Most polymers self-organize into mesophases possessing intertwined lamello-columnar morphologies, resulting from the simultaneous coexistence of lamellar and columnar sublattices. The successful preparation of oriented thin films of several of these polymeric homologues allowed further investigations by atomic force microscopy, transmission electron microscopy, electron diffraction, and grazing-incidence SAXS, which provided a deeper insight of the intricate supramolecular organizational modes, including the complete elucidation of the structure of the lamello-columnar mesophases. This simple and versatile strategy provides a route to elaborate polymeric materials incorporating two intercalated separate pathways toward charge carrier transport, of paramount importance for future electronic and optoelectronic applications.