Rustum Roy recently observed that, operating from a finite number of elements, materials science faces an over-supply problem, too many scientists, and too few elements. Like all Malthusian dilemmas, relief is unlikely within the assumptions. Materials scientists, however, enjoy opportunities to develop new materials through morphological engineering of traditional substances. Carbon, after all, provided a century of progress for polymer chemists and a revolution in the manufacturing world. The trend from atomic- to molecular- to chain-level engineering can obviously be extended to mesostructure engineering and beyond. The tailoring of porosity is an example of such an extension.
This issue of the MRS Bulletin examines the concept of engineered porosity from three perspectives. Smith, Hua, and Earl discuss characterization based on classic gas adsorption and more recent NMR and scattering methods. Two articles, one by Harold and Lee, and the other by Fain, look at the pore structure requirements for important applications, reactive separations and gas separation. Finally, the materials science of engineered porosity is discussed in four articles. Even describes emulsion-derived foams in which surface-active species impose micron-scale structure that is retained during polymerization. Shapovalov broadly reviews methods to introduce porosity in metals. Durian discusses recent work on relaxation phenomena in aqueous foams. Finally, I review the factors that control structure in mesoporous aerogels.