outside developments in the future. At the same time, increased contact between polymer workers and those in outside fields will ensure that new techniques developed within polymers will be rapidly exploited in those outside fields where they are useful.

THEORY, MODELING, AND SIMULATION

Enormous opportunities and new needs for polymeric materials exist in the rapidly expanding and internationally competitive high-technology areas, such as the information industry, aerospace industry, and biotechnology. Realizing these opportunities and meeting the needs for novel materials, however, depend on a much deeper understanding of polymeric materials than has been necessary for developing commodity polymers in the traditional chemical industry.

Theory and computations can help provide this deeper understanding. They reduce large collections of experimental observations to working knowledge, rules, patterns, models, and general understanding. They explain experimental observations; they correlate data from different materials and phenomena; and, in general, they quantify and unify our knowledge. More importantly, theory provides new predictive capabilities to guide the development of new ideas and to direct experimental efforts in exploring new chemical structures, processes, and physical properties.

In favorable cases, theory and simulation can reduce the amount of experimental work required or even eliminate it entirely. For example, one of the classical theoretical problems is to predict ''phase diagrams," diagrams that describe the resulting states of matter and the conditions when polymers and solvents are mixed together. This is a central problem in the design of new materials. Modern polymeric materials often involve mixtures of several different types of polymers, of different molecular weights, and in complex solvents at different temperatures and pressures. They involve many variables. Such variables determine the difference between achieving a successful material with appropriate optical, thermal, mechanical, and chemical stability properties or producing a useless mixture. To find optimal conditions could require exploring 5 or 10 variables in detail, which could require tens of person-years of experiments. Instead, theoretical or computational models often permit the exploration of many different variables quickly, and thus they reduce the amount of time to develop new materials by an enormous factor.

Another example of the use of theory and simulation is in the area of polymer processing. Many companies currently model (1) kinetics of polymerization reactions and (2) fabrication, combining phenomenological rheological and heat transfer characterization of the polymer, to assess a proposed design before cutting a mold or die. Extensive efforts have been devoted to modeling fabrication operations such as extrusion, mixing, and molding operations. Once a process configuration has been selected, computer-based models are generally able to



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