Small-angle x-ray scattering experiments conducted with compositionally asymmetric low molar mass poly(isoprene)-b-poly(lactide) diblock copolymers reveal an extraordinary thermal history dependence. The development of distinct periodic crystalline or aperiodic quasicrystalline states depends on how specimens are cooled from the disordered state to temperatures below the order-disorder transition temperature. Whereas direct cooling leads to the formation of documented morphologies, rapidly quenched samples that are then heated from low temperature form the hexagonal C14 and cubic C15 Laves phases commonly found in metal alloys. Self-consistent mean-field theory calculations show that these, and other associated Frank-Kasper phases, have nearly degenerate free energies, suggesting that processing history drives the material into long-lived metastable states defined by self-assembled particles with discrete populations of volumes and polyhedral shapes.

Self-consistent field theory (SCFT) is a powerful tool for the design and interpretation of experiments on block polymer materials. In this Perspective, we lower the barrier to entry to the use of SCFT by experimental groups by two means. First, we present a pedagogical introduction to an improved version of the open-source Polymer Self-Consistent Field (PSCF) software package and of the underlying theory. Second, we discuss methods for generating robust initial guesses for the fields that are computed in SCFT. To demonstrate our approach, we present two case studies in which a typical desktop computer has been used to simulate the structure of (i) body-centered cubic, face-centered cubic, A15, and Frank–Kasper σ sphere-forming phases of a diblock copolymer melt and (ii) two core–shell morphologies of ABAC tetrablock terpolymers. A companion Web site provides all of the relevant software and detailed instructions for reproducing all results contained herein.

Picking up at the conclusion of Viovy's review of the physics of gel electrophoresis [J.-L. Viovy, Rev. Mod. Phys. 72, 813 (2000)], this review synthesizes the experimental data, theoretical models, and simulation results for DNA electrophoresis in microfabricated and nanofabricated devices appearing since the seminal paper by Volkmuth and Austin [Nature (London) 358, 600 (1992)]. Prototype versions of these devices separate DNA by molecular weight at a rate far superior to gel electrophoresis. After providing an overview of the requisite background material in polymer physics, electrophoresis, and microfluidic device fabrication, the focus is on the following three generic problems: (i) collision with an isolated post, (ii) transport in an array of posts, and (iii) entropic trapping and filtration in the slit-well motif. The transport phenomena are examined here in the context of the length and time scales characterizing the DNA, the device, and the applied electric field.