Solution processability endows polymer semiconductors with several intriguing prospects, from low-cost processing, such as inkjet printing, to the possibility of creating new materials by simply mixing solutions. Polymer blends have already been exploited in light-emitting diodes (LEDs) [1] and photovoltaic diodes, [2,3] as well as light-emitting electrochemical cells (LECs), [4] although the factors controlling their supramolecular structures [5] and properties are not fully understood. Most polymer blends undergo phase segregation. [6] This has been used to generate large-area heterojunctions, [2] but it can be detrimental where solid solutions are sought to increase photoluminescence (PL) efficiency, and where rough surface morphology is a problem. Here we use three supramolecular strategies to prepare a complex material that has none of these drawbacks and benefits from enhanced electroluminescence properties: firstly, ionic interactions favor mixing of a conjugated polyelectrolyte with poly(ethylene oxide), PEO, preventing phase segregation and boosting the PL efficiency; secondly, the PEO facilitates ion transport and allows fabrication of LEC-like devices which display a two orders-of-magnitude increase in the electroluminescence (EL) efficiency; thirdly, threading the conjugated polymer through cyclodextrins gives higher PL efficiencies at small PEO loadings, and increases the EL efficiency over the full range of PEO concentrations. Insulated molecular wires, IMWs, consisting of conjugated polymers threaded through cyclodextrin rings (b-CD-poly(paraphenylene) (b-CD-PPP), b-CD-poly(fluorene) (b-CD-PF), a-CD-poly(4,4′-diphenylene vinylene) (a-CD-PDV), and b-CD-poly(4,4′-diphenylene vinylene) (b-CD-PDV); Fig. 1) are versatile supramolecular architectures [7] that display a reduced degree of interchain interactions reflected in higher electroluminescence efficiency, blue-shifted absorption/emission, and reduced luminescence quenching and packing density, when compared to their uninsulated analogues (PPP, PDV, and PF). [8] In this paper we exploit their polyelectrolytic nature, and use the presence of lithium carboxylate and sulfonate substituents to drive the formation of supramolecular complexes with polymers featuring ion-coordination properties. This supramolecular assembly enables us to reduce the tendency of the different components to phase separate, to promote smooth surface morphologies, and to boost the PL and EL efficiency. The interaction of PEO with polyrotaxanes in aqueous solution was tested by fluorescence titration, using b-CD-PDV and PDV. This experiment revealed that both conjugated polymers bind PEO strongly even under extremely dilute conditions (1 ppm PEO by weight, ca. 1 × 10 -8 mol dm -3 of both components). The fluorescence spectra of PDV at a range of PEO concentrations are shown in Figure 2a, and the corresponding titration curve is plotted in Figure 2b (see Fig. S1 in the Supporting Information for analogous data for b-CD-PDV). The titration curves for b-CD-PDV and PDV fit remark...

A molecular wire consisting of a metal/molecule/metal junction can be regarded as the basic building block for future nanoelectronics applications. Alongside the great effort expended in the last ten years on the use of single molecules as electroactive components, [1][2][3] there is also a growing interest centered on the use of supramolecular architectures as electroactive species to bridge metallic electrodes.[4] The supramolecular approach can enhance the mechanical and electronic properties of the wire, which should improve the performance of electronic devices.[ [5][6][7][8][9][10] One major challenge in the study of charge transfer across organic molecules is achieving reproducible attachment between metallic electrodes. Although different electrode pairs have been employed, including break junctions, [3] lithographically tailored nanoelectrodes, [11] and a solid substrate and a conductive tip of an atomic force microscope [12][13][14] or a mercury drop, [15] new, scalable routes to the controlled incorporation of nanometer-scale objects in the gap between nanoelectrodes are required. The manipulation and alignment of an anisotropic object using dielectrophoretic forces in an electric field has been successfully accomplished with a variety of different structures including metal and semiconducting nanoparticles [11] and nanowires, [16] DNA molecules, [17] carbon nanotubes, [18,19] block copolymers, [20] ZnO-organic complexes, [21] and dendron rod-coil ribbons. [22] This has recently led, for example, to improved emission properties of single conjugated polymer molecules.[23] The possibility of applying this technique to supramolecularly engineered nanostructures is thus of major interest in view of their reversible self-assembling properties under external stimuli such as temperature and chemical environment. [24] We provide here the first direct quantitative determination of the electric-field-assisted alignment of single organic supramolecular fibers self-assembled at a surface. We have chosen a gel-forming functionalized 1,3,5-triamide cis,cis-cyclohexane derivative (cyclohexane trisamide gelator (CTG), Fig. 1a) that is known to self-assemble into supramolecular fibers in aqueous solution through the formation of hydrogen bonds. [25,26] Due to its wider applicability for electronic applications, we present here attempts to form similar fibers in an organic solvent. Fibers were deposited from solution onto two gold electrodes arranged in a source-drain geometry with micrometer-scale separation. During deposition, a DC voltage was applied between the two electrodes and the system was cooled below its sol-gel transition temperature (T sol-gel ).In the gel, the three intermolecular hydrogen bonds among the amide moieties of CTGs are both parallel to one another and perpendicular to the plane of the cyclohexane ring (see Fig. 1a inset), endowing strong, self-complementary, and uniaxial intermolecular interactions that are necessary to enforce quasi-1D self-assembly.[27] Since each hydrogen bond has a dipolar...