Macromolecular Science and Engineering: Future Directions and Opportunities, Study notes of Chemistry

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1 Human Repair. Courtesy of National Geographic and Corel Corporation. 2 Cell Membrane Interactions with Electronic Materials. Courtesy of Aaron Amstutz, Beckman Institute, Urbana, Illinois. 3 Genetically Modifiable Plants for Polymer Synthesis. Courtesy of Crop Sciences, University of Illinois. 4 Towering Blown Film. Courtesy of Chris Macosko, University of Minnesota and Rheometric Scientific. 5 Polymer Light-Emitting Diodes. Courtesy of Conjugated Polymer Group, Linköping University. 6 ß-Sheet Assembly in Macromolecular Crystals. Courtesy of David Tirrell, University of Massachusetts. 7 Supramolecular Mushroom Nanostructure. Courtesy of Samuel Stupp and Aaron Amstutz, Beckman Institute, Urbana, Illinois. 8 Metallocene Catalyst. Courtesy of Robert Waymouth, Stanford University. 9 Self Assembly of Cone-Shaped Polymers into Nano-spheres. Courtesy of Virgil Percec, Case Western Reserve University.

NSF M ACROMOLECULAR WORKING G ROUP

C HAIR : ANDREW J. L OVINGER (DIV. OF M ATERIALS RESEARCH )

D IV. OF MATERIALS R ESEARCH : D AVID L. N ELSON, G. B RUCE TAGGART, L.D. H ESS

D IV. C HEMISTRY: M ARGARET A. C AVANAUGH , G EORGE M. R UBOTTOM

OFFICE OF MULTIDISCIPLINARY ACTIVITIES IN MATHEMATICAL AND PHYSICAL SCIENCES :

H ENRY M. B LOUNT, III

OFFICE OF SCIENCE AND T ECHNOLOGY INFRASTRUCTURE: R OBERT R EYNIK

D IV. OF C IVIL AND MECHANICAL SYSTEMS: R OBERT M. W ELLEK , M ARIA K. B URKA,

V IJAY JOHN

D IV. OF ELECTRICAL AND C OMMUNICATIONS SYSTEMS: A LBERT B. H ARVEY, R AJINDER KHOSLA

D IV. OF ENGINEERING EDUCATION AND C ENTERS : J OHN C. H URT, TAPAN K. M UKHERJEE

D IV. OF MANUFACTURING AND I NDUSTRIAL INNOVATION: K ESH N ARAYANAN

D IV. OF M OLECULAR AND C ELLULAR BIOSCIENCES : K AMAL SHUKLA , M ARCIA STEINBERG ,

P HILIP D. H ARRIMAN

D IV. OF BIOLOGICAL I NFRASTRUCTURE: G ERALD B. S ELZER

D IV. OF ADVANCED C OMPUTING I NFRASTRUCTURE AND R ESEARCH : R ICHARD S. H IRSCH

D IV. OF GRADUATE EDUCATION: PAUL W. J ENNINGS

D IV. OF U NDERGRADUATE EDUCATION: S USAN H. H IXSON , M ARGARET P. W EEKS

D IV. OF INTERNATIONAL PROGRAMS : B ONNIE H. T HOMPSON, J EANNE H UDSON

I NTER-A GENCY LIAISONS ON MACROMOLECULAR SCIENCE AND E NGINEERING

R ICHARD D. K ELLEY (D EPARTMENT OF ENERGY)

B ARBARA KARN (ENVIRONMENTAL P ROTECTION AGENCY)

D OUGLAS J. K ISEROW (ARMY R ESEARCH O FFICE)

ELENI KOUSVELARI (N ATIONAL INSTITUTES OF H EALTH)

C HARLES Y. C. L EE (AIR F ORCE O FFICE OF SCIENTIFIC RESEARCH )

L ESLIE E. S MITH (N ATIONAL I NSTITUTE OF STANDARDS AND TECHNOLOGY)

TERRY ST. C LAIR (N ATIONAL AERONAUTICCS AND SPACE ADMINISTRATION)

K ENNETH J. W YNNE (OFFICE OF N AVAL R ESEARCH )

JOHN WATSON (NATIONAL INSTITUTES OF HEALTH)

Table of Contents

• Preface.....................................................................................................................
• Executive Summary.................................................................................................
• Workshop Program..................................................................................................
• Biomaterials and Macromolecular Biology - Summary............................................
• Human Repair .........................................................................................................
• Intelligent Junctions between Cells and Computers................................................
• Bio-inspiration from Spider Silk................................................................................
• Biomaterials and Macromolecular Biology - Subgroup Report................................
• Novel Macromolecular Structures - Summary.........................................................
• Polyethylene............................................................................................................
• Designed Materials from Nano-Bricks.....................................................................
• Novel Macromolecular Structures - Subgroup Report.............................................
• Macromolecular Science and Engineering and the Environment - Summary.........
• Plastics from Plants.................................................................................................
• Report...................................................................................................................... Macromolecular Science and Engineering and the Environment - Subgroup
• Innovation in Polymer Processing - Summary.........................................................
• Stopping the Bubble’s Dance..................................................................................
• Innovation in Polymer Processing - Subgroup Report............................................
• Translating Macromolecular Discoveries into Technologies - Summary..................
• LEDs........................................................................................................................
• Powerful Polymers...................................................................................................
• Report...................................................................................................................... Translating Macromolecular Discoveries into Technologies - Subgroup
• Appendix I................................................................................................................
• Appendix II...............................................................................................................

and Dr. John W. Lightbody (Acting Director, Div. of Physics.) In the Directorate for Engineering, Dr. Elbert L. Marsh (Acting Assistant Director), Dr. Joseph E. Hennessey (Acting Deputy Assistant Director), Dr. Gary W. Poehlein (Director, Div. of Chemical and Transport Systems), Dr. Janie M. Fouke (Director, Div. of Bioengineering and Environmental Systems), Dr. Bruce M. Kramer (Director, Div. of Design, Manufacturing, and Industrial Innovation), and Dr. Ronald L. Sack (Director, Div. of Civil and Mechanical Systems.) In the Directorate for Biological Sciences, Dr. Mary E. Clutter (NSF Assistant Director), Dr. James L. Edwards (Deputy Assistant Director), Dr. Maryanna P. Henkart (Director, Div. of Molecular and Cellular Biosciences), Dr. Bruce L. Umminger (Director, Div. of Integrative Biology and Neuroscience.) In the Directorate for Education and Human Resources, Dr. John B. Hunt (Deputy Assistant Director), Dr. Karolyn K. Eisenstein (Senior Staff Associate, Div. of Undergraduate Education), and Dr. Herbert H. Richtol (Program Director, Div. of Undergraduate Education.) In the Directorate for Social, Behavioral, and Economic Sciences, Dr. Norbert M. Bikales (Head, NSF Europe Office.) I apologize if I inadvertently left out anyone else. Most importantly, I am extremely thankful to Andrew Lovinger for his dedication and commitment to this project. Finally, I would like to acknowlegde Verna Riley and Jeff Dalsin for their help in prepar- ing this report.

Samuel I. Stupp Workshop Chair

April 1998

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Executive Summary

A very exciting new field of interdisciplinary macromolecular science and engineering (MMSE) is rapidly emerging, a field at the crossroads of materials science/polymer sci- ence, engineering disciplines, chemistry, physics, and biology. MMSE is the area of sci- ence and engineering that studies substances composed of very large molecules such as those found in common plastics but also in biological structures, including genes and proteins. The origin of the field is the narrower area of polymer science and engineer- ing which grew over the past four decades around plastics technology. At the end of this century it is clear that our knowledge base in a number of disciplines including polymer science, chemistry, biology, and engineering is converging to initiate a new field that can exert a profound impact on the nation’s economy and quality of life.

• The interdisciplinary field of MMSE will have a critical presence in 21st century chem- ical, pharmaceutical, biomedical, manufacturing, infrastructure, electronic, and infor- mation technologies. All new industries and businesses that will bridge information age technology and our rapidly growing knowledge base in biology require novel develop- ments in MMSE. Interdisciplinary MMSE will also play a critical role in the develop- ment of nanotechnologies since macromolecules are themselves nano-sized objects that can have great structural diversity.
• Major molecular design achievements in macromolecular structures have occurred over the past decade in catalysis, molecular and cell biology, nanotechnology, and supramolecular materials science. Future exciting developments in MMSE are there- fore expected at the interfaces of polymer science with the frontiers of other disciplines.
• New types of research and educational innovation are needed to translate recent and future macromolecular discoveries into technologies. The proactive role of NSF and other funding agencies is particularly critical at this time given the recent downsizing of industrial research infrastructure.
• Research and educational efforts in the following areas need to be strongly supported in order to develop frontier interdisciplinary MMSE in the U.S.
• Connections between cells and computer hardware could deliver new types of envi- ronmental sensors, medical diagnostic equipment, and probes of biological objects such as viruses and bacteria. Macromolecules hold the key to create such connec- tions because cell receptors are essentially polymers embedded in the cell mem- branes. Novel structures also need to be discovered to create contacts between syn- thetic and biological macromolecules.
• The ideal materials to repair humans have not been discovered yet and are not likely

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involving the global environment.

• Research must be supported on the possibility of using plants or microbes to synthe- size technologically useful macromolecules. It is also necessary to support research on benign processing and synthesis of macromolecules in water or carbon dioxide instead of organic solvents.
• Research must also be pursued in the use of macromolecular materials to assist in environmental remediation and cleanup. One example is macromolecules with high specificity to remove toxic metals from water.
• It is also important to study the interaction of polymers with ecosystems, covering the areas of toxicity, hormonal activity, and other health related effects.
• Because of recent advances in the synthesis of novel macromolecular architectures and supramolecular chemistry, there are new opportunities to be identified on biodegradable polymers. There are also new varieties of processing and new materi- als to be discovered that could withstand multiple exposures to recycling.
• Processing innovation for macromolecular products is critically needed for the novel technologies that will involve self assembly and supramolecular chemistry. There is essentially no knowledge base in this area.
• Novel processing techniques will be needed for molecularly designed biomaterials, biomedical technologies, and for the new environmentally benign macromolecular compositions. Processing in fully benign environments will become an area of increas- ing interest.
• The great increase in polymer architectures made possible by recent synthetic advances requires a rational modeling approach to processing in order to take full advantage of the new diversity in structures and their relations to realistic processing flows. This modeling also needs to explore in situ correlations of microstructure devel- opment under flow conditions.
• Innovative polymer processing techniques must be developed to structure thin films, fibers, and foams by application of external electric/magnetic or substrate fields. New methods must also be developed to achieve rapid and precise microscale and nanoscale patterning of macromolecular products.

General Recommendations

The workshop participants hope that NSF and other agencies will insure optimal devel-

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opment of this critical field of interdisciplinary MMSE in the U.S. by funding both research and educational initiatives that specifically target the areas mentioned above. These ini- tiatives should include flexible modes of funding and proposal evaluation procedures to minimize the burden on the community.

• There is need to establish inter-agency agreements or initiatives to grow interdiscipli- nary MMSE programs that serve the missions of multiple agencies. One example would be a partnership between NSF and NIH in order to establish programs that tar- get the area of novel biomaterials for the repair of human tissues.
• In order to promote development of macromolecular science related to environmental problems, biomaterials, and innovative manufacturing, a special effort must be made to enhance coordination among appropriate NSF programs in physical sciences, bio- logical sciences, and engineering.
• In all scientific areas, education should be closely integrated with research. Creative educational approaches should be explored at all levels to train a new generation of interdisciplinary scientists who will need to be versed in the chemical, physical, biolog- ical, and engineering aspects of this field. The need to integrate these multiple aspects at all levels of education is particularly critical for the effective development of interdis- ciplinary MMSE.

EXECUTIVE S UMMARY • 7

9

Dr. Joseph Wirth, “Converting Polymer Science into Technology”

Coffee break

Subgroup discussions

Dinner

Subgroup discussions

Thursday, May 15

Subgroup discussions

Coffee break

Plenary Session , Samuel I. Stupp, Chair

Recommendations from Subgroup 1 and discussion, Prof. Robert Grubbs

Recommendations from Subgroup 2 and discussion, Dr. Scott Milner

Recommendations from Subgroup 3 and discussion, Prof. Lynn Jelinski

Recommendations from Subgroup 4 and discussion, Prof. David Tirrell

Recommendations from Subgroup 5 and discussion, Prof. Edwin Thomas

Lunch

Subgroup meetings to draft reports

Adjourn

Friday, May 16

Discussion of Workshop results by Organizing Committee

Coffee break

Meeting of Organizing Committee

Lunch

Meeting of Organizing Committee; draft of Report

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Human Repair

For decades macromolecules in many different forms have played a key role in human repair. Blood vessels have been repaired with fabrics woven from fibers made of poly(ethylene terephthalate) — the same polymer found in beverage bottles and magnetic tapes. In recon - structed hip and knee joints, the most technologically common plastic — poly - ethylene — is used as the low friction surface that allows patients to move their limbs without pain after surgery. Very recently macromolecular artificial skins that are partly biodegradable have been developed for victims of serious burns. Many other examples in current use could be cited. Novel concepts in human repair using macromolecules are being researched in laboratories around the world, and one interesting example is the tissue engineering approach to regenerate diseased or broken bones, torn cartilage in our knees, and other structures. This approach utilizes sponge-like materials made of biodegradable macromolecules that are seeded with cells and proteins that could, in principle, regenerate the tissue of interest. Through research the future could deliver much more sophisticated concepts in human repair using molecu - larly designed macromolecular materials that interact with tissues in the body in a pre-engineered way. These novel forms of macromolecular matter could be designed to form perfect junctions with natural tissues and function as ideal replacements for parts of the human body in need of repair. Other forms will be cell seeded and biodegradable in a prescribed time, and would be able to change size and shape predictably to make way to the regenerated tissues they template as scaffolds. The contact of cells with nanoscale features on the

Human repair in the future will be done either with spe- cially designed synthetic materials (right side) or with materials that will mediate the regeneration of tissues (left side.)

B IOMATERIALS AND MACROMOLECULAR B IOLOGY • 13

scaffolds could regulate some of their func - tions, thus curing diseases, dissolving tumors, and mediating the growth of miss - ing tissues. Those advances will require nanoscale control of macromolecular struc - ture, a deeper understanding of self assem - bly, advances in molecular biology, and access to genetically engineered proteins.

B IOMATERIALS AND MACROMOLECULAR B IOLOGY • 15

Bio-inspiration from Spider Silk

Why spider silk?

Spider silk is a protein fiber with unusually good mechanical properties. Single fibers of spider dragline silk, about 1/15 the diameter of a human hair, have a tensile strength that rivals that of steel, yet the fibers stretch to more than 10% elongation before breaking.

Spider silk also combines a rea - sonably high stiffness with a very large extension to break, so that the toughness — the energy required to cause a tensile failure — is very high. The initial modu - lus of the fiber is greater than that of nylon-6,6, and more importantly, the fiber does not fail in compression by kinking, a feature that makes spider silk in some ways superior to the highest performance human-made fibers.

In addition, the mechanical prop - erties are achieved under extremely mild and environmentally benign processing conditions, and without extensive draw - ing of the fiber, unlike synthetic high per - formance fibers.

Finally, the spider system is ideal as a research vehicle because it repre - sents a set of evolutionarily tailored fibrous materials. Most of these materi - als are poorly understood and hold many insights to be discovered regarding struc - ture-function relationships and process - ing relevant to materials science.

Why now?

The tools of biotechnology now make it possible to produce genetically engineering silk-like proteins. Once the molecular basis for the excellent mechanical properties of silk is under-

Scientists are looking toward spider silks as a source of bio-inspiration for the production of a new class of high performance materials.

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stood, we can produce synthetic DNA that codes for the correct sequences and express the proteins in bacteria or perhaps even in plants. There are still hurdles to overcome, though. One involves learning how the spider processes the fibers to pro - duce a highly oriented material, and some - how imitating that process in the laborato - ry. Another involves understanding the effect that water has on the mechanical properties, and engineering out of the pro - tein these deleterious effects.