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Highly uniform and conductive single crystals of poly(3-hexylthiophene) (P3HT)-based homo and block copolymers with the end coily blocks of polystyrene, poly(methyl methacrylate), and poly(ethylene glycol) are developed using self-seeding method from varied quality solvents. Edge-on and flat-on orientations are detected depending on the thickness and width of single crystals. Coily blocks are excluded from the P3HT crystalline structures, leading to brush-like or hairy regions on surface of grown single crystals in the longitude of P3HT chains. The larger single crystals possessing flat-on orientation are obtained from weaker solvents at higher seeding temperatures. The longer P3HT chains are folded, however, the shorter backbones are laminated on each other. The highest backbone lamination occurs for homo-P3HT7150 ( Mn of P3HT = 7150 g mol−1) single crystals grown at 20 °C from anisole, the weakest employed solvent. In contract, highly ordered and folded hairy single crystals are acquired from better solvents and high molecular weight P3HTs. In these conditions, the crystallographic features of the hairy block copolymer single crystals are similar to those of nonhairy homo-P3HT ones. The coily brush-covered P3HT48 800 single crystals have more foldings compared to the homo-P3HT48 800 ones, whereas only two laminated backbones in shorter P3HT blocks are detected. [ABSTRACT FROM AUTHOR]

The phenomenon of restrained stress-induced preferential orientation of S′ precipitates is investigated using a single-crystal of Al–1.23Cu–0.43 Mg alloy. Al–1.23Cu–0.43 Mg single-crystal specimens are subjected to stress aging, and the microstructure is analyzed by transmission electron microscopy (TEM). It is found that the stress-induced preferential orientation of S′ precipitates is restrained owing to the dislocations produced by a higher stress. The effect of dislocations on the oriented precipitates depends on the total length of the intersection lines for precipitate habit planes and dislocation glide planes. This investigation not only provides important insight into solving the anisotropy problem attributed to precipitation strengthening, but also offers a benchmark for choosing the appropriate stress range in manufacturing of Al–Cu–Mg alloys. [ABSTRACT FROM AUTHOR]

The early stages of recrystallization have been systematically characterized in single crystal metals of medium and low stacking fault energy. Goss {1 1 0}〈0 0 1〉 and brass {1 1 0}〈1 1 2〉 oriented samples of Ni, Cu and Cu–2 wt.% Al alloy were deformed in a channel die to a logarithmic strain of 0.51 to develop a homogeneous structure composed of two sets of symmetrical primary microbands and then lightly annealed. Scanning electron microscopy/electron backscattered diffraction analyses demonstrate a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations. The disorientation angles across the recrystallization front are mostly grouped in the ranges of 25–35° and 45–55° around axes located near, but not at, the normals of all four {1 1 1} planes. The original nuclei possess disorientation angles of 25–35°. The orientation of the growing new grain quickly transforms through the formation of a first generation twin, leading to disorientations of 45–55°. The most frequent situation occurs when the normal of the twinning face plane is situated near the rotation axis, around which the crystal lattice of the “primary nuclei” rotates. Based on the anisotropy of grain growth, a possible mechanism of orientation generation and grain growth by thermally activated movement of dislocation families on {1 1 1} planes is proposed. [ABSTRACT FROM AUTHOR]