Polymers (1995)

The Naval Research Laboratory (NRL) maintains a broad-based program of research and development that serves to ensure that the Navy will have advanced technological capability when it is needed. NRL has an active program in polymers, and the relevance of this work to Navy needs is direct and evident. As is often generally true of advances in science and technology, much of the research done at NRL also benefits the civilian domain.

It should be noted that the panel was not charged with reviewing and evaluating NRL programs, but rather was asked to identify research opportunities. The remainder of this chapter briefly discusses frontiers in polymer science and engineering, and Chapter 2 discusses polymer research opportunities for NRL. Appendix A summarizes current and promising polymer research topics, Appendix B outlines present and potential future uses of polymers by the Navy, and Appendix C describes briefly the panel's understanding of polymer research in progress at NRL.

The National Research Council (NRC) recently released the results of a comprehensive assessment of the polymer science and engineering field in the report Polymer Science and Engineering. The Shifting Research Frontiers (National Academy Press, Washington, D.C., 1994). Many of that study 's main findings and conclusions are summarized below. Although the target audience for the present report (i.e., the Naval Research Laboratory) is much more specific than that for Polymer Science and Engineering, there is almost complete commonality of relevance on the research side and much that is pertinent in regard to applications. Thus the material in this report is closely related to the content and conclusions of Polymer Science and Engineering.

Basic research in polymers is a major area of opportunity, highlighted by the following:

• Synthetic methods are needed to provide more precise control of polymer compositions, and a number of promising techniques are being pursued, e.g., coordination catalysis, biocatalysis and enzyme synthesis, ring-opening metathesis, group transfer polymerization, hybrid organic-inorganic materials synthesis, and dendritic polymer preparations. Nature offers examples of precise polymer synthesis at good rates and mild conditions, and it remains for research to gain the understanding required to bring the fruits to commerce.

• Polymer theory is another central aspect of current and future research. The recent revolutionary advances in computer power offer opportunities in modeling and simulation of structures, processes, and properties that were undreamed of a decade ago. The states of matter exemplified by polymers (including solutions, crystalline and amorphous morphologies, fibers, liquid crystals, and blends) will be classified and understood through the power of new theory supported by computation. Rheological behavior, mechanical properties, and electronic characteristics will become predictable by computation. Processing of polymers will be carried out by machines operating under total computer control. It is clear that these advances in understanding and control will be based on the combination of new theoretical methods (e.g., force-field and coarse-

grained simulations) and improved computer hardware and software.

• Polymer characterization is a field that has profited greatly from advances in instrumentation and computation. Recent progress and opportunities are based on major improvements in traditional techniques and the introduction of new methods that are well adapted to the study of polymers. Examples include two-dimensional nuclear magnetic resonance (NMR), which has become a premier method for determining sequence distribution; several high-resolution microscopic techniques that are specifically suited to the study of dielectric surfaces and can be used without the requirement of high vacuum (e.g., near-field scanning optical microscopy); significantly improved scattering methods for solid-state, blend, and solution work, and advanced surface characterization techniques. Characterization methods are the basic tools that support the entirety of polymer science and engineering. No program can be at the forefront without broad-based access to and use of the most advanced methods.

• Research is also needed to broaden the applications of polymeric materials. Materials with “tailored” properties based on blends, high-strength fibers, new matrices for composites, and improved stability of toughening additives are finding new uses as materials substitutes and in unique applications. This trend will accelerate as failure mechanisms become better understood. The areas for substitution of materials span automobiles, aircraft, boats, construction, machinery, and many other specialty items. While military applications are growing (e.g., body armor, uniforms, and aircraft), the field is ripe for rapid growth and penetration by polymeric materials.

• Polymers are abundant in biological materials and are increasingly important in health, medicine, and biotechnology. Examples include implants, medical devices and diagnostics, controlled drug release, biological methods and mechanisms, and the techniques of biotechnology. This is an area of rapidly expanding understanding and application.

• Even in electronics polymers are widely employed as dielectrics, resists, chip packaging, and electrophotographic media, and new applications of polymers are based on their electronic properties (e.g., synthetic metals, batteries, nonlinear optical materials, light-emitting diodes, displays, and holographic materials). All of these applications require research and development activity to ensure successful market performance.

• Polymers may be employed in ways that are favorable from the standpoint of environmental acceptability. Polymers are generally environmentally benign, and research on recycling and disposal is progressing. Generally, polymers should be regarded as part of the environmental solution, not the problem. However, research on environmental aspects of polymers must be continued to ensure responsibility in materials choices. Environmental concerns are also of increasing importance to the Navy because of the need to comply with the MARPOL agreement, which restricts, and in some cases forbids, the earlier practice of disposal of refuse by dumping into the sea.