We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Multi-scale ordering of materials is central for the application of molecular systems in macroscopic devices. Self-assembly based on selective control of non-covalent interactions provides a powerful tool for the creation of structured systems at a molecular level, and application of this methodology to macromolecular systems provides a means for extending such structures to macroscopic length scale. Monolayer-functionalized nanoparticles can be made with a wide variety of metallic and non-metallic cores, providing a versatile building block for such approaches. Here we present a polymer-mediated 'bricks and mortar' strategy for the ordering of nanoparticles into structured assemblies. This methodology allows monolayer-protected gold particles to self-assemble into structured aggregates while thermally controlling their size and morphology. Using 2-nm gold particles as building blocks, we show that spherical aggregates of size 97 +/- 17 nm can be produced at 23 degrees C, and that 0.5-1 microm spherical assemblies with (5-40) x 10(5) individual subunits form at -20 degrees C. Intriguingly, extended networks of approximately 50-nm subunits are formed at 10 degrees C, illustrating the potential of our approach for the formation of diverse structural motifs such as wires and rods. These findings demonstrate that the assembly process provides control over the resulting aggregates, while the modularity of the 'bricks and mortar' approach allows combinatorial control over the constituents, providing a versatile route to new materials systems.

The wavelength of light represents a fundamental technological barrier to the production of increasingly smaller features on integrated circuits. New technologies that allow the replication of patterns on scales less than 100 nm need to be developed if increases in computing power are to continue at the present rate. Here we report a simple electrostatic technique that creates and replicates lateral structures in polymer films on a submicrometre length scale. Our method is based on the fact that dielectric media experience a force in an electric field gradient. Strong field gradients can produce forces that overcome the surface tension in thin liquid films, inducing an instability that features a characteristic hexagonal order. In our experiments, pattern formation takes place in polymer films at elevated temperatures, and is fixed by cooling the sample to room temperature. The application of a laterally varying electric field causes the instability to be focused in the direction of the highest electric field. This results in the replication of a topographically structured electrode. We report patterns with lateral dimensions of 140 nm, but the extension of the technique to pattern replication on scales smaller than 100 nm seems feasible.

We report on structural investigations of a series of regioregular poly(3-hexylthiophene) with well-defined molecular weight (5-19 kg/mol) using DSC, small angle and wide-angle X-ray scattering, and AFM. With increasing temperature, we identify three ordered phases, namely 3D crystalline, 2D crystalline with disordered side chains, and a layered phase of smectic symmetry, followed by complete melting. Although all samples crystallize in extended chain conformation, the lower molecular weight material exhibits a lower crystallinity, most likely caused by noncrystallizable end groups. The crystallinity increases strongly with increasing molecular weight, which could be a possible explanation for the known dependence of charge transport properties on molecular weight.

Polymers offer unique avenues for the structural control of materials on the nanoscopic length scale for the production of nanoporous media, membranes, lithographic templates, and scaffolds for assemblies of electronic materials. [1±4] With structures on this length scale, quantum properties of electronic materials are exhibited even at elevated temperatures. The natural length scale of polymer chains and their morphologies in the bulk lie precisely at these length scales and, as such, there is a substantial effort to produce, characterize and use polymeric nanostructures. The ease of processing polymers adds to the attractiveness of polymer-based nanostructures. In comparison to the time-intensive process of sequential writing of nanoscale patterns, nanostructure formation by self-assembly is highly parallel and inherently fast. Block copolymers are ideal materials in this respect, since, due to the connectivity of two chemically distinct chains, the molecules self-assemble into ordered morphologies with a size scale limited to molecular dimensions. Of particular interest are block copolymers that form cylindrical microdomains, since the elimination of the minor component transforms the material into an array of nanopores.A prerequisite for the use of copolymers is the control over the orientation of the microdomains. In particular, for cylindrical microdomains, an orientation normal to the substrate surface is desirable. Two different approaches are used to this end. In thin films, random copolymers anchored to a substrate can be used to produce a neutral surface. [5] For entropic reasons, the microdomains orient normal to the substrate surface. [6] In a second approach, electric fields were used to orient the cylindrical microdomains parallel to the field lines. [7±10] The approach relies on the orientation-dependent polarization energy induced when an anisotropic body is placed in an electric field. An anisotropic microphase structure will orient such that the interfaces between the two blocks are aligned parallel to the electric field.In this article it is shown that cylindrical microdomains of a copolymer film can be used to generate an array of ordered nanoscopic pores with well-controlled size, orientation, and structure. To this end, selective etching procedures and a characterization of the samples by quantitative analysis of the X-ray scattering along with electron (EM) and atomic force microscopies (AFM) are described. The processes outlined are shown to be operative over a very large range in sample thickness ranging from 40 nm up to several micrometers. The resulting nanoporous films are promising candidates as membranes with specific transport properties and as templates for electronic and magnetic nanostructured materials. Figures 1A and 1B show AFM images obtained from a 40 nm±thick film prepared on a neutral substrate after annealing. Cylinders standing perpendicular to the substrate are clearly discernable, particularly in the phase image, since the height variations are very small. Polystyr...