Polymer Materials Science: Novel Synthesis and Characterization of Supermolecular Structures
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sidérable p o t e n t i a l in electronic or photonic applications. The issues addressed by thèse two authors are timely. For example, the National Research Council Report, Materials Science and Engineering for the 1990s (published in 1989), sounded a strong cry for novel approaches to new materials and for new, créative particip a n t s to join the effort. A p r e v i o u s NRC report, Frontiers in Chemical Engineering Research, identified numerous research o p p o r t u n i t i e s in electronic and photonic materials and drew spécial a t t e n t i o n to the i m p o r t a n c e of understanding the interface. Most recently, the National Science Foundation declared in an open letter dated March 8,1991 that in FY 1992 it intends to initiate a new research thrust supp o r t e d by t h r e e NSF D i r e c t o r a t e s (Mathematical and Physical Sciences; E n g i n e e r i n g ; and Biological, Behavioral, and Social Sciences) that will emphasize fundamental u n d e r s t a n d i n g and applications of synthesis and processing methods for new and existing m a t e r i a l s . I n i t i a l e m p h a s i s will be placed on novel electronic, photonic, and biomolecular materials. I would like to place the articles by Tirrell and Knoll in a suitable context. Tirrell's article emphasizes how imp r o v e d or u n i q u e p o l y m e r m a t e r i a l p r o p e r t i e s a r i s e as s u p e r m o l e c u l a r
structure becomes enhanced when statistical control of the polymerization process is replaced by more directed synthetic routes. Knoll introduces the subject of u l t r a t h i n p o l y m e r films, their fabrication, and représentative a r e a s of a p p l i c a t i o n to p r o v i d e appréciation of the breadth of information obtainable from evanescent wave techniques. The biological linkage in Tirrell's article is paramount to the research he reports, but Knoll also considers examples of biopolymer Systems. This linkage was an important considération in selecting thèse authors to increase visibility of biomolecular materials among the materials community. General polymer science textbooks describe the synthetic routes to high polymers through classical catégories based on mechanism (step growth versus chain growth) or structure (condensation versus addition). A key feature of thèse processes is statistical control of the polymerization. This is manifested in a spread of the length of the polymer chains produced in a homop o l y m e r i z a t i o n , or in t h e c o m p o s i tional variation in a copolymerization. The broadening trends of statistical control can be partly countered in certain cases. For example, Ziegler-Natta polymerization, based on the discovery of particular organometallic catalyst Systems, allows excellent control of stereoregularity. Although this is limited to relatively few monomer types, it is of major industrial importance in polyolefin p r o d u c t i o n . A second example of e n h a n c e d control emerged from the discovery of anionic polymerization, in which "living" polymers a
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