Poly(aryleneethynylene)s (PAE) are easily synthesized, chemically stable, and color-responsive towards their surroundings. These superbly chromic polymers are attractive as active transducers in sensors and advanced organic electronic devices. PAEs are generally fluorescent with emission maxima ranging from 420-600 nm, and can be either water-or organo-soluble. PAEs from linear building blocks are rigid rod molecules and display a host of supramolecular arrangements in solution and in the solid state. The poly(para-phenyleneethynylene)s (PPE) are lyotropic or thermotropic smectic liquid crystalline. In the solid state, PPEs display lamellar supramolecular structures that lead to distinct stranded nanoscale morphologies. The spectroscopy and the optical properties of the PAEs and in particular of the PPEs are dominated by their conformation, which is influenced by solid-state packing, solvent, temperature and other factors. The presence of twisted and planar forms and their interconversion leads to attractive structure/property relationships; PAEs are of use as ingredients for advanced supramolecular materials.