PerspectiveMaterials Science

Recasting Metal Alloy Phases with Block Copolymers

Science  15 Oct 2010:
Vol. 330, Issue 6002, pp. 333-334
DOI: 10.1126/science.1196698

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Crystalline order develops through a balance between short-range attractive and repulsive interactions (1) that not only operate on atoms but work at the nanoscale on supramolecular structures (2). Spherical particles often pack together into simple, high-symmetry arrangements, but more complex topologically close-packed structures, such as the Frank-Kasper σ phase (3, 4) first seen in metal alloys, have also been observed (see the figure, panel A). Spherical supramolecular aggregates formed from polymers and monodisperse branched macromolecules (57) can be used to mimic atoms and explore how these phases arise. On page 349 of this issue, Lee et al. (8) show that linear block copolymers that form spherical aggregates through microphase separation can crystallize into a Frank-Kasper σ phase. Relative to metal alloys, the volume of its crystalline repeating unit, the unit cell, is six orders of magnitude greater (see the figure, panel C). The scaling up of atomic lattices by using spherical supramolecular aggregates is also of practical interest because such structures could be used as photonic materials (9), nanoreactors (5), or drug delivery vehicles (10).