ONR Research Opportunities in Chemistry (1994)

One of the great challenges in materials science is to understand the connection between the atomic- and molecular-scale composition of matter and macroscopic properties, and to manage this connection to achieve desired properties through chemical synthesis. Much of the strength of materials science comes from its ability to provide unique properties—that is, properties or combinations of properties not provided by existing materials. Continuing, simultaneous advances in microscale measuring techniques, chemical synthesis, physical chemistry, and computation and simulation make it increasingly possible to imagine the rational design of materials that have desired, useful properties. The rational design of materials that have specified function is an enormously broad activity. The most promising approach would be one focused on invention of new materials. There are well-understood paradigms for development of new materials, once they exist: invention, however, is risky but is also a very highly leveraged activity, especially if the properties chosen fit with clearly appreciated needs. The following topics illustrate the opportunities in this field.

1. Sensors.  A broad range of tasks depend on a capability for sensing chemicals: protection against chemical agents, monitoring of environmental quality, and process control are examples important to the Navy. Understanding the response of many sensor types at a detailed molecular level lags successful application and limits the design of new sensors. An existing challenge is to find sensors that are robust, interference free, and usable over a wide range of conditions. The payoff will be high: enablement of process control and regulation of environmental contaminants.

2. “Smart” materials.  This trendy name describes a class of materials that are transducing; that is, the material responds to a change in some environmental parameter with a change in properties: photochromic glasses and piezoelectric solids are two examples. Although the idea of a smart material is easy to enunciate, defining a set of guidelines for the design and synthesis of smart materials has largely been difficult and slow. The situation is now ripe for progress in this area.

3. Photonic materials.  Materials with nonlinear optical properties represent a particularly appealing class of materials to examine. These have potential to be useful in a range of optical switches and modulators. The optical properties of molecules can now be calculated with some accuracy; inference of the optical properties of materials is blocked by many shortcomings, especially an inability to predict crystal structures from molecular structures, and to estimate the magnitudes of cooperative interactions between molecules.

4. Gels and elastomers.  Gels and elastomers represent a unique state of matter. New uses are opening for gels as sensors, actuators, and dampers. Gels are important in a wide range of applications, including diffusion media and mechanical transducers based on the gel

collapse phenomenon. Designing these materials to have desired properties —moduli, optical properties, high-temperature stability—would open doors to a range of new types of functions.

5. Magneto-resistive materials.  Materials that demonstrate the “giant magneto resistive effect” (GMRE) are important to the future of high-density magnetic information storage devices. These materials will most certainly find wide use in the read-elements of sensors for such devices. At this time, the GMRE materials that have been studied are heterogeneous mixtures and alternating layered structures of ferromagnetic and conducting metals. The origin of the GMRE is not fully understood at this time. Establishment of a sound theoretical basis for the origin of the effect will provide chemists with the information necessary to rationally design materials with the range of properties required for use in the sensor elements of storage devices and will allow rapid optimization of these properties. The panel encourages support of work that will provide a theoretical foundation for and an understanding of the materials-properties relationships in this new and interesting class of materials. The search for organic and metal-organic analogues could prove rewarding.

A number of advances are required in basic science to accomplish the design of materials.

1. Crystal engineering.Many applications of materials require unique crystalline states. The ability to design (or control) a molecular crystal by designing the molecules from which it is formed is just beginning to develop. Substantial work is also required in understanding the science and technology of the growth of high-quality single crystals.

2. Parallel computation. Computation and simulation of the properties of extended solids or glasses—especially of complex organic molecules—is limited by the quality of the potential functions that are available and by the speed of the computation. Both would benefit from a much improved capability to use parallel computation. Basic studies in the design of new algorithms for parallel computation relevant to the simulation of solid and glass structures represent an area of special opportunity.