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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century Executive Summary CONTEXT AND OVERVIEW Researchers in the chemical sciences synthesize and process materials by manipulating chemical reactions and physical transport. This ability to construct materials from molecular components, combined with the ability to manipulate materials for function, has blurred the line between chemistry and materials science. Similarly, as the chemical sciences have developed materials and devices to explore biological processes and used biologically inspired self-assembly to create materials from molecular building blocks, the boundaries with biochemistry and molecular biology have also been blurred. Advances in synthesis and processing of materials continue to have significant impact on emerging fields such as biotechnology, information technology, and nanotechnology. Materials with tailored functionality (such as high strength, electronic, or optical properties) are critical to modern technologies. For example, high speed computer chips and solid state lasers are complex, three-dimensional composite materials built by organizing chemical entities with nanometer precision through the application of synthesis procedures. As advances on materials continue, chemical resolution on the nanometer scale will be required. As a result, better preparation of both new and existing materials is needed, along with preparations that are cost effective and have minimal environmental impact. Particularly in the field of nanotechnology, advances in synthetic techniques such as new vapor, liquid, and solid catalytic reactions will be needed. In addition, new self-assembly methods offer opportunities for “bottom up” synthesis of materials from their molecular constituents. The ability of the chemical sciences to modify and predict molecular struc-
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century tures and the emerging understanding of self-assembly, promises a revolution in new materials with properties thus far only predicted by theory. Decisions about the development and implementation of new materials will ultimately be based on cost versus benefit for our society. A strong competitive advantage can be gained in materials development from an efficient iteration between molecular alterations of a chemical or material and the processes by which the chemical or material is “engineered” into the final product. DISCOVERY As new materials requirements become more complex, materials chemistry is increasingly turning toward the discovery of new materials and methodologies. Methodologies continue to take advantage of pure serendipity and trial and error approaches, but they are significantly enhanced by new approaches such as combinatorial synthesis, high-throughput screening, and molecular computations. In the past several decades, the chemical sciences have made large strides in the development of novel and useful materials. The development of thermoplastics and/or structural polymers has had an increasing influence on a range of applications, particularly in construction and national defense. New polymers have led to such devices as low current/low power polymer-based displays. Moreover, polymers for drug delivery and tissue engineering are beginning to benefit the biomedical field. Catalysis has been an especially fruitful area of research in the energy and transportation sector, with the catalytic converter being the ubiquitous example of novel catalysis benefiting society broadly through reduced air pollution. The development of metallocene catalysts is leading to high-strength polyethylene for multiple applications, ranging from grocery bags to light weight armor. Photoresist, a photochemically active polymer, has made it possible to define with nanometer accuracy the complex patterns that form the backbone of computer chip production. New advances are being made in organic-based electronics that might be useful in a variety of applications, including large-area displays, memories, sensors, and identification tags. Three-dimensional photonic crystals with complete photonic band gaps at optical telecommunication wavelengths are expected to result in revolutionary optically integrated photonic circuits for computers and telecommunication systems. Materials chemistry is drawing on a wide range of means to develop new compounds and applications. Design by analogy is perhaps the most common method used to produce new materials. The development of new inorganic nanoscale materials by analogy with biological systems is just one example of this approach. Future materials technologies are going to require molecular structures of increasing complexity and precision composition that is greater than that possible today. Materials will have to be tailored from the molecular level to the macroscopic device in order to achieve the functionality required by advanced technological applications. Molecular self-assembly inspired by biological syn
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century thesis may hold the key to new routes useful to future technologies. Because most processes for synthesis by analogy presently remain imprecise, high-throughput methods of synthesis and analysis offer another promising alternative to conventional cycles of design, re-evaluation, and redesign. The rapid increase in computing power continues to have considerable impact on analytical and computational methods. Molecular simulations, previously limited by both computing power and accuracy, now enable scientists to understand and design complex systems at the molecular level. The development of new instrumentation is essential in both materials characterization and in exploring potential applications. For example, scanning probe microscopy has enabled greater understanding of materials at the nanoscale and has enabled materials of this size to become active components in functional devices. The relative roles of “needs-driven” and “discovery-driven” research in materials science and engineering will always be an important consideration. While it may seem that “materials discovery” must lie in the latter area, there is considerable room for discovery in the fields of chemistry and chemical engineering on materials that have clear links to future technologies. The continued health of materials research will require fundamentally new insights into the behavior of materials (whether or not applications are identified at the outset) as well as developments driven by clearly articulated technological and market needs. Important research programs can mix these two kinds of objectives in many different ways, resulting in a broad spectrum of activities that is likely to lead to breakthroughs. Finding: Materials discovery occurs via many routes. A diverse portfolio of interdisciplinary research efforts directed toward discovery of new materials systems is likely to produce significant advances in this field. Finding: Renewed and expanded emphasis on synthesis, catalysis, and processing methods will be essential to continuing advances in materials science and technology. Finding: Recent developments in combinatorial synthesis, high-throughput screening, and molecular-based computation of materials offer substantial promise as adjuncts or alternatives to more traditional programs of design, evaluation, and re-design. INTERFACES Materials chemistry is interdisciplinary by nature. Cooperative efforts between materials chemistry and other disciplines have given rise to many of the synthetic materials introduced over the course of the twentieth century. Advances in new materials often result from work on a specific or perceived need in several different areas. As a result, materials chemistry is closely linked to materials
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century science, physics, biology, medicine, along with many other fields. Work at the interfaces among these disciplines represents some of the most exciting and challenging areas of scientific inquiry today and raises expectations of significant technological impact in the future. Scientists and engineers of all backgrounds need to better understand the various disciplines—the language of each, how to work with each other, and how to fund and reward collaborative activities. Work at the interface between materials chemistry and medicine over many decades has brought innumerable advances that we take for granted today. Materials that can be implanted into the body and remain for many years without adverse effects require understanding of the biological processes around the material and reactions that the material may undergo in the body once implanted. Collaborations at this interface have led to the development of special-purpose metal alloys and polymer coatings to prevent the body from rejecting prosthetic bone replacements. Materials chemistry has also had a significant impact on separations technologies such as hemodialyzers, blood oxygenators, intravenous filters, and diagnostic assays. Biocompatible polymeric materials have been developed for controlled delivery of drugs, proteins, and genes. Extensive work continues on new materials for medical diagnostics and particularly medical sensors. In the future, research in materials chemistry might include in situ drug production, cellular systems, and human integrated computing. It is certain that new sensors that take advantage of the latest developments in materials will be essential for health and national defense. The role of chemistry is so embedded in structural materials that it is almost taken for granted. For example, the materials in modern cars and airplanes that make them safer, lighter, and more fuel efficient than their predecessors result from advances in materials synthesis and processing. Coatings on structural materials, whether to inhibit corrosion, protect, beautify, or serve some other purpose, are also the products of materials chemistry—as is the adhesion of these coatings to the base material. The identification of appropriate combinations of materials in a composite and optimization of processing conditions require a detailed understanding of the underlying chemical processes. In the future, structural materials will incorporate sensing, reporting, and even healing functions into the body of the material. Such “smart materials” will require integration of dissimilar materials, which can only be achieved through collaborations across the many disciplines involved. Chemistry has had a tremendous role in developing the materials and processes forming the basis for advanced computing, information, and communications technologies. The modern chip fabrication facility is essentially a chemical factory in which simple molecular materials are transformed into complex three-dimensional composites with specific electronic functionality through the use of chemical processes such as photoresist, chemical vapor deposition, and plasma etching. Two exciting future directions are the migration of electronic and optical organic materials and realization of analogous control of light via photonic lat
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century tices such as what we have today in electronics. The development of photonic circuits and optical computing is yet another possible example of an area enabled by the chemical sciences that requires multidisciplinary approaches. Dramatic progress will be required on many fronts, including materials chemistry, to achieve both improved quality of life and improved environmental quality. Life cycle engineering, the process of reducing excess waste throughout the production process, will require the development of environmentally benign materials as well as the development of sustainable processing and disposal methods. Materials chemistry will also continue to contribute to the safety of our food supply by the development of new packaging materials, which can be expected to incorporate sensors to indicate spoilage or unsafe storage conditions Finding: Materials that are self-diagnosing, self-repairing, and are multifunctional would potentially be of great value in many applications. Finding: Materials chemistry is basic to technological developments. Advances will require close interaction between scientists and engineers working in diverse fields. CHALLENGES Fundamental chemical research creates the infrastructure that enables technologies key to the health and well-being of our communities. Therefore, research must focus on future challenges and how solutions to those challenges will affect society as a whole. As the world’s population continues to grow and the standard of living improves, environmental concerns in developing nations grow exponentially. In the drive to alleviate diminishing resources, a key challenge is to develop new technologies that enable affordable clean energy. Materials chemistry is already critical to the development of photovoltaics, solar cells, and fuel cells. The development of new recyclable and biodegradable materials will also become an important challenge as environmental concerns increase. Another challenge is to use chemistry to create new materials utilizing the insights obtained by studying biological structures, by functionally integrating cells and bio-molecules into materials, for example. The results might include miniaturized, multifunctional biosensors and human-computer interfaces. We might also be able using living systems as a means to synthesize and process materials with intricate structures, such as the silicates made by marine species. Fundamental understanding will be necessary to control matter on all length scales (nano-, micro-, and macro-) as well as at all steps in the self-assembly processes. For any given application, knowledge of materials properties and function from the atomic scale to the macro-scale – 18 orders of magnitude in length and time scales is necessary. Proper analysis of materials is essential in augmenting the field of materials science. The challenge is the development of instruments for high-resolution,
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century three-dimensional, element-specific mapping that are non-destructive and provide real-time information on both hard and soft materials on multiple scales. It is necessary to understand how technological advances and scientific breakthroughs relate to society in a global context. Technological developments must be increasingly efficient, considering issues such as the globalization of sourcing and manufacturing. Almost every technology that has been discussed or that can be envisioned is likely to have a direct impact on the future challenges facing mankind as a whole. Finding: Advances in materials chemistry will be essential for simultaneously improving the standard of living and environmental quality. Finding: The design of tailor-made materials with defined performance attributes is a grand challenge. Finding: A grand challenge in materials chemistry is to create new materials utilizing the insights obtained by studying biological structures. Finding: New analysis techniques will be required to enable significant progress in materials chemistry. INFRASTRUCTURE As research into new materials continues, it is important to recognize that today’s problems represent a challenge to our current infrastructure. The benefits of a healthy infrastructure are numerous. A broader and more efficient research structure will serve to feed the competitive engine while developing new areas of research. Infrastructure also involves education at all levels. At the university level, it is important to note that fields of study are changing rapidly and that research in the chemical sciences, particularly on new materials, is becoming increasingly interdisciplinary. Providing students with the tools needed to learn about specific topics in other disciplines and to communicate effectively in these fields will be essential. Effective investment in both instruments and maintenance, particularly in regional cooperation for instrument use, will help to limit redundancies in local research capabilities and ultimately may save money for the universities and businesses involved. Basic research, applied research, development, and demonstration play a role at all levels in the development of new materials. If academic researchers develop an understanding of the needs for and applications of new materials in the marketplace, important problems are examined almost inevitably. If there is a tight feedback loop between discovery and the end user, research teams will be better able coordinate their efforts and see a higher rate of return on technology development.
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Materials Science and Technology: Challenges for the Chemical Sciences in the 21st Century Industry increasingly finds itself unable to support basic research. As a result, the health of the chemical sciences will depend largely on the basic molecular science done in universities and national labs. Great care must be exerted to ensure that truly novel, high-risk, yet high-quality works are supported at the federal level. Finding: Instrumentation has always played an important role in materials research, and new tools for fabrication and analysis will continue to move the field forward. Finding: Chemical scientists are called upon increasingly to communicate with scientists in many other disciplines, and must learn to do so effectively.
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