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Preface Nature can provide an impressive array of polymers that can be used in fibers, adhesives, coatings, gels, foams, films, thermoplastics, and thermoset resins. Polymers from renewable resources take on new importance in a world that is trying to navigate through the apparent conflict between technological development and environmental protection. It is ironic that the solutions to the problems plaguing the environment must come from the re-direction of the problem creators. Unfortunately, for too long, technological development was not linked to principles of environmental ecology. Our society has evolved so that technology lies at the core of economic development. So, we now turn to the technology innovators to create new pathways to products that are harmonious with environmental maintenance and renewal. This book is dedicated to these ideas and principles. Biological processes are remarkable because they reside in an allaqueous environment, function in a continuous or seamless manner, and may be conducted under ambient conditions. This is in stark contrast to most synthetic materials preparation and processing, which often require organic solvents and high temperatures and pressures. There is also generally insufficient consideration for biodégradation or recycling to replenish starting feedstocks. In the biological world, post-biosynthesis tools are used to facilitate processing. Examples worth exploring and exploiting are the formation of mesophases, enzymatic processing to control recognition events, surfactant-polymer interactions to optimize molecular recognition at interfaces, chiral control to dictate secondary and higher order structures, and cross-linking to convert water soluble precursors to water-insoluble composites and complexes. Finally, material-lifecycle concerns suggest that a great deal can be learned from biological paradigms, where all materials are returned to natural geochemical and biochemical pathways once their use is completed. Polymers from renewable resources are produced by biological processes and, therefore, benefit from the above characteristics of natural processes. Developments in the field of polymers that exploit in-vitro enzyme-based processes continue to expand. Important new insights into novel reactions, reaction mechanisms, changes in enzyme structure in organic solvents, the use of neat reactions to generate polymers using enzymes, and molecular evolution of enzymes are all examples of this expansion. The biological world builds and xi In Biopolymers from Polysaccharides and Agroproteins; Gross, Richard A, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.
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modifies all of its polymers using enzymes. Enzymes provide many critical controls important to their use in polymer science including: (1) control of polymer structure (e.g., enantioselectivity and regioselectivity, (2) simple reactions over an ever-widening range of conditions (e.g., extremes of temperature, p H , pressure, and salt), (3) important options in green chemistry, and (4) rapid enzyme evolution (e.g., use of D N A shuffling and error prone P C R techniques). This book includes recent work where in-vitro enzymecatalysis was used to synthesize oligosaccharides, star-shaped heteroarm polyesters, and new vinyl monomers from glycolipids. The surfactant and emulsifier industry in the United States has grown nearly 300% during the past decade. In 1989, the U.S. production was estimated to be 15.5 billion pounds and the value of U.S. shipments in 1989 was approximately 3.7 billion dollars. Many of the applications of surfactants and emulsifiers (desorption of organic pollutants from soil, dispersants in cleaning formulations, facilitate emulsion formation, etc.) either involve human contact or release into the environment. Therefore, there is a critical need for a new generation of natural, low toxicity, fully biodegradable products. This book includes a chapter that describes natural polymers that are useful as surfaceactive agents for the control of soil erosion. In addition, powerful natural emulsifiers from microbial fermentation are the topic of one chapter. The interface between biology and polymer science is a rapidly emerging research theology that involves the seamless convergence of concepts, ideas and research tools at the interface between biology and polymer science. Work at this interface is growing at a rapid pace and is expected to make major contributions to science in the new millennium. Scientists having core training in microbiology, genetic engineering, biophysics, agricultural science, plant physiology, food science, and other biological disciplines bring new tools, molecules, and fresh ideas to the fields of polymers and materials science. In return, polymer chemists and materials scientists bring to their colleagues in biology expertise in chemistry, materials design, structural analysis, processing, polymer solution properties, solid-state polymer physics, and an array of different characterization tools. The synergy gained by working between these fields is marvelous and exciting. What is desparately needed is a new generation of scientists who have sufficient information at the interface to begin feeling comfortable to bridge the gap between these disciplines. Many of the authors of chapters within this book describe research that has benefited by interactions at the biology-materials interface. Water-soluble polymers are widely used in industrial products including food and beverages, cosmetics, toiletries, adhesives, coatings, pulp and paper, textiles, water treatment, detergents, and surfactants. In the United States, the quantity of these polymers used is estimated to be in excess of 13 billion pounds per year, a volume approaching that of packaging plastics. Water-soluble polymers, synthesized from readily renewable resources, can biodegrade rapidly upon disposal and produce harmless natural substances. For xii In Biopolymers from Polysaccharides and Agroproteins; Gross, Richard A, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2001.
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example, a-,p-poly(D,L-aspartate), is currently under development as a water soluble detergent additive to replace non biodegradable poly(acrylate) and related polymers. Unfortunately, cost factors are still obstacles that limit the successful implementation of this and other related new polymers that seek to replace billions of pounds of non-biodegradable polycarboxylates. The persistence in nature of down-the-drain water-soluble products is of great concern. Over time, recalcitrant water-soluble products can accumulate and may cause changes to the ecosystem. The fact that such polymers are not "seen" as they accumulate makes them less noticed by the public that might otherwise raise objections. Numerous chapters in this book describe water-soluble polymers from natural sources such as amino acids and native or modified polysaccharides. The commercial success of product synthesis by fermentation routes depends in part on the better use of inexpensive agricultural by-products such as starch, molasses, soap-stock oils, and others. Genetic methods now exist that allow extraordinary improvements in strains. Metabolic-engineering of metabolic pathways expands the range of low/no-cost carbon sources that can be converted efficiently to products. In addition, engineered strains are leading to new options in the design and control of product structure, and, therefore, properties. Biodegradable polymers are at an exciting stage of development and positioned to play important roles. Excellent basic and applied research in this field and Increased global regulatory pressure have spawned the formation of new fledgling industries, which are creating safe biodegradable packaging materials for widespread public use, specifically designed for composting. In addition, new water-soluble degradable polymers have been developed that degrade in wastewater treatment facilities. This book highlights recent developments in biodegradable polymers. Featured topics include the establishment of regulatory guidelines, eco-labeling of products, product marketing and positioning, development of test-methods to study polymer biodegradability, and the establishment of disposal/composting infrastructure for biodegradable polymer disposal. The papers from this book were contributed by authors that participated in the 7th Annual Meeting of the Bio/Environmentally Degradable Polymer Society, held August 19-22, 1998 at the Royal Sonesta Hotel in Cambridge, Massachusetts, as well as the symposium on Polymers from Renewable Resources, held at the annual American Chemical Society Meeting, August 23-27, 1998, in Boston, Massachusetts. O f course, this book would not have been possible without the wonderful contributions by the book chapter authors. In addition, we are grateful for the help from Ann Wilson and Kelly Dennis of the A C S Books Department who made sure that this project came to a successful completion. I am also indebted to my wife Wendi, who provides the moral support and the
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time that is inevitably extracted from "family hours" that went into the editing and other tasks to complete this volume. RICHARD A. GROSS
Professor and Herman F. Mark Chair Department of Polymer Chemistry Polytechnic University Brooklyn, NY 11201
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C A R M E N SCHOLZ
Department of Chemistry University of Alabama at Huntsville John Wright Drive M S B 333 Huntsville, AL 35899
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