Synthesis, processing, and manufacture of solid materials form a continuum of intellectual and technological activities. The boundaries between these three elements of materials science and engineering are becoming increasingly blurred as the need for strong coupling between basic research and applied technology becomes more and more clear.
A practical reason for this blurring is the frequent need to choose synthetic reactions in such a way that products are suitable for further processing. For example, in the preparation of ceramics, it is generally desirable that the synthetic reactions produce precursor particles that are small enough to be compacted easily and sintered at relatively low temperatures. Another reason for the blurred distinction is that modern techniques for preparing materials often are direct combinations of what we conventionally have considered to be separate operations of synthesis and processing. A pertinent example here is the reactive injection molding of polymers in which the synthetic chemical reactions occur simultaneously with the “process” of molding. In this appendix, the focus is on activities that seem to the committee to fall primarily in the category of “synthesis.” Discussion of topics that are primarily “processing” is saved for the appendix with that title. The reader should keep in mind that this distinction may sometimes appear to be artificial.
Most of the major innovations in materials technology of the past two centuries have depended directly on the development of novel synthetic routes to existing or new materials. For example, in the early part of the nineteenth century, metallic aluminum was a curiosity available only in very small quantities. With the new synthetic route from cryolite developed by Hall, aluminum became a major commercial material. The field of synthetic polymers had its beginnings at the turn of the twentieth century with the development by Baekeland of phenol formaldehyde resins. However, the real revolution in this field began in the 1930s with synthesis of thermoplastics such as nylon, polyethylene, and polyester, which could be processed directly into film, fibers, or molded plastics. The plastics revolution, which has influenced every aspect of our lives, was made possible by novel synthetic approaches to both the monomers and the polymers. Thus synthesis not only has led to new and novel materials but also has provided low-cost alternatives that have made products affordable.
Rapid growth of the chemical industry in the 1950s and 1960s was so dependent on synthesis of new materials that most chemical companies maintained R&D centers consisting primarily of synthetic chemists. However, starting in the mid-1960s, some profound changes have occurred in U.S. industrial research that have altered sharply the way materials-related industries can respond to competitive challenges or generate new opportunities.