Substantial successes have been achieved in these areas, but many aspects of polymerization in organized media remain poorly understood. It has been suggested that confinement of functional groups to a lattice or in two-dimensional arrays may either enhance or reduce reactivity, but the evidence for such effects is, with few exceptions, anecdotal. As materials science seeks control of structure and properties on shorter and shorter length scales, polymerization in anisotropic phases is sure to take on increasing importance.
A related area of investigation concerns polymeric structures held together by non-covalent forces, for example, by hydrogen bonds. Although they are significantly weaker than covalent bonds, hydrogen bonds exhibit directional character and are therefore useful in controlling both the size and the shape of molecular aggregates of dimensions comparable to those of polymer chains. Penetrating studies of molecular recognition processes in organic chemistry are providing new strategies for the assembly of large-scale structures, and it is clear that a broad view of polymer synthesis, a view that embraces both covalent and non-covalent bond-forming steps, should be encouraged.
The last decade has witnessed advances in the control of macromolecular architecture. Nevertheless, important challenges remain, particularly with respect to the control of chain sequence. New synthetic approaches to controlled architecture, including the use of biological methods, should be vigorously pursued.
Polymer synthesis, both on the laboratory scale and in manufacturing, is still largely a series of stepwise conversions, from feedstocks, to monomers, to polymers, to products. The development of more highly coupled, integrated syntheses, in which advanced materials are derived efficiently from simple feed-stocks, will depend in large part on research on new catalysts and new catalytic reactions.
The demands of new technologies will continue to place a premium on the synthesis of high-performance polymers, that is, on polymers of unprecedented thermal or mechanical properties. Continued efforts to design, prepare, and evaluate such materials must be accorded high priority.
Polymer science in general—and polymer synthesis in particular—must embrace a broader view of the field, in which both covalent and non-covalent interactions are exploited to maximum advantage. This view will create lively exchanges of information and ideas between practitioners of polymer science and workers in related areas of organic and inorganic chemistry, biology, physics, engineering, and materials science. Work at these disciplinary interfaces should be supported and pursued.
Environmental issues in polymer synthesis, as in other areas of polymer science, will continue to grow. Environmentally sound synthetic methods, strategies