This issue of MRS Bulletin is devoted to the subject of supramolecular materials. The term supramolecular is widely used to describe the intentional use of noncovalent interactions to bring about a desired arrangement of molecules. As the articles in this issue illustrate, this type of molecular engineering can provide structural control on the nanoscale and beyond, broadly impacting the properties of the resulting materials. The goal is to create a collection of molecules in which the whole possesses characteristics that are different and unattainable from the individual components.

The notion of micromachines made up of miniature gears and motors may seem like a fairy tale. In 1959, Richard Feynman delivered a lecture entitled “There's Plenty of Room at the Bottom,” a bold prediction of what was to come in the future, where one could fit the entire Encyclopaedia Britannica onto the head of a pin or use ions focused through a microscope lens in reverse to etch away silica to create patterns on a submicron scale. In retrospect, Feynman's hypotheses were amazingly accurate. He was describing the techniques of microlithography and the manipulation of atoms by scanning tunneling electron microscopy, methods that are commonplace today. Advances in biochemistry have revealed the enormous complexity of “simple” organisms, leading one to conclude that “micromachines” (of a complexity that a visionary giant such as Feynman had foreseen) have long been operating quite happily without any assistance from chemists!

The design of inorganic and organic solids with novel structures and properties has long been the object of materials research. The classical examples of porous materials (i.e., involving reversible guest passage) are zeolites. First discovered in the mid-1700s, zeolites are hydrated, crystalline aluminosilicates that organize into stable, discrete frameworks. Basic structures employ tetrahedral atoms (silicon or aluminum) bridged by oxygen atoms, where each oxygen is shared between two metalloid tetrahedra. Resulting covalent lattices can be neutral or negatively charged (as a result of bridging oxides) and often employ alkali metal or alkalineearth counterions. As a consequence of this ordered structure, zeolites both benefit from and are limited by their highly geometrical nature: their rigid structures are inherently robust, yet they are difficult to process. In addition, while natural and unnatural zeolites have been characterized, harsh synthetic conditions are common to both and lead to limitations in design and processability. Even so, these impediments have not prevented constructing a myriad of architectures on zeolite host lattices. Strengths and weaknesses aside, zeolites demonstrate a major objective of materials chemistry: the ability to manifest macroscopic physical properties based on embedded microscopic structure.

One of the goals of contemporary science is the atomic or molecular design of materials in order to achieve specific properties. There is special interest in imitating with these designed materials the remarkable integrated functionality we see in biology. Soft matter offers a particularly good opportunity to realize these goals because of the vast structural space offered by organic systems.

What started as a scientific challenge roughly 10 years ago has become a technological reality today, as materials from supramolecular polymers and their many applications as smart materials have emerged. Synthetic polymeric materials are among the most important classes of new materials introduced in the 20th century. They are primarily used for construction, but electronic and biomedical applications are also at the forefront of science and technology.

The increasing demands of miniaturization in the microelectronics industry has forced continual improvement in the materials that are used in the fabrication of semiconductor devices. Advances in photoresists for microlithographic applications have reduced the feature size to 0.25 µm and below, and this drive to eversmaller features, coupled with the introduction of copper, has placed increasing demands on the dielectric material. Materials with lower dielectric constants (depicted in dark gray in Figure 1) are therefore required to more efficiently insulate these submicron features, such as the copper interconnect lines used to connect the transistors and memory cells in these advanced multilevel devices (Figure 1). This allows the minimization of crosstalk, signal delays, and power consumption. While vapor-deposited silicon dioxide and other derivatives are currently being employed, they suffer from unacceptably high dielectric constants (ε > 3.6) and are unacceptable for future generations of microelectronic devices.