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The long‐range order of spherical block copolymer films is greatly improved if the underlying surface has been etched to form wells and mesas. Epitaxial growth of polystyrene/poly(2‐vinylpyridine) block copolymers on SiO2 with structures 1–10 μm wide yields single‐crystal‐like structures on top of the mesas (see Figure), and in the wells, provided the height of the mesas exceeds one layer of copolymer spheres (27 nm). (See also inside front cover.)

Developing a better understanding of the evolution of morphology in plastic solar cells is the key to designing new materials and structures that achieve photoconversion efficiencies greater than 10%. In the most extensively characterized system, the poly(3‐hexyl thiophene) (P3HT):[6,6]‐phenyl‐C61‐butyric‐acid‐methyl‐ester (PCBM) bulk heterojunction, the origins and evolution of the blend morphology during processes such as thermal annealing are not well understood. In this work, we use a model system, a bilayer of P3HT and PCBM, to develop a more complete understanding of the miscibility and diffusion of PCBM within P3HT during thermal annealing. We find that PCBM aggregates and/or molecular species are miscible and mobile in disordered P3HT, without disrupting the ordered lamellar stacking of P3HT chains. The fast diffusion of PCBM into the amorphous regions of P3HT suggests the favorability of mixing in this system, opposing the belief that phase‐pure domains form in BHJs due to immiscibility of these two components.

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Well-ordered mesostructured silica and titania films were prepared using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer species (Pluronic P123) as the structure-directing agents. By varying the volume ratio between the copolymer and inorganic components of the precursor solution, silica and titania thin films with cubic, 2D hexagonal, and lamellar mesostructures were prepared. The regions over which the three phases were obtained correspond well with those of the water-block copolymer binary phase diagram when considered in terms of the volume fraction of copolymer incorporated. In particular, a cubic mesostructure with crystalline TiO 2 (anatase) in the walls, stable to 400 °C, was synthesized.

The manufacture of smaller, faster, more efficient microelectronic components is a major scientific and technological challenge, driven in part by a constant need for smaller lithographically defined features and patterns. Traditional self-assembling approaches based on block copolymer lithography spontaneously yield nanometer-sized hexagonal structures, but these features are not consistent with the industry-standard rectilinear coordinate system. We present a modular and hierarchical self-assembly strategy, combining supramolecular assembly of hydrogen-bonding units with controlled phase separation of diblock copolymers, for the generation of nanoscale square patterns. These square arrays will enable simplified addressability and circuit interconnection in integrated circuit manufacturing and nanotechnology.

A record high OFET hole mobility, as high as 23.7 cm(2) /Vs, is achieved in macroscopic aligned semiconducting polymers. The high mobility is insensitive to the polymer molecular weight. Polymer chains are aligned along the fiber to facilitate intrachain charge transport.

The fracture toughness (characterized by the critical energy release rate Gc) of interfaces between polystyrene (PS) and poly(2-vinylpyridine) (PVP) reinforced with poly(styrene-6-2-vinylpyridine) was measured with a double cantilever beam test geometry. The effect of the PVP block degree of polymerization (Wpvp) and the areal density of block copolymer chains at the interface (2) on the measured Gc and on the fracture mechanisms was investigated quantitatively. The PS degree of polymerization (Alps) was kept >280, while Alpvp was varied between 45 and 870. For Afpvp below 200 the interfaces showed only a small increase in Gc with increasing 2 and failed by pull-out of the short PVP chain. In this regime Gc increases linearly with 2 and scales roughly with New2, in reasonable agreement with a recently proposed model of failure by chain pull-out.1 If Npw was increased well above 200, corresponding roughly to the average molecular weight between entanglements for the PVP, two separate fracture mechanisms could be distinguished. At low values of 2, Gc increased only slowly with 2 and the interfaces failed by scission of the copolymer chains near the joint between the two blocks. At higher values of 2, the interfaces fractured by first forming a stable craze ahead of the propagating crack tip, giving rise to much higher values of the measured fracture toughness.In this regime, Gc scaled with 2,^, an areal density of chains with at least one "effective" entanglement, in very good agreement with a model recently proposed by Brown2 for failure by craze fibril breakdown.