Hermann Staudinger

German chemist

• Born: March 23, 1881
• Birthplace: Worms, Germany
• Died: September 8, 1965
• Place of death: Freiburg im Breisgau, West Germany (now in Germany)

Staudinger became the founder of a novel branch of chemistry when he conceived of and proved the existence of macromolecules. This work laid the foundation for the technological achievements in the plastics and high polymer synthetics industries. In addition, Staudinger contributed to the fields of organic chemistry and molecular biology.

Early Life

Hermann Staudinger (HEHR-mahn SHTOW-dihnj-ur), the winner of the 1953 Nobel Prize in Chemistry, was the son of Auguste Staudinger and Franz Staudinger, a neo-Kantian philosopher. Staudinger’s primary education took place at a local gymnasium in Worms from which he was graduated in 1899. When he began his secondary education at the University of Halle, he was interested in botany; however, he switched his major to chemistry on the advice of his father, who had been told that his son must first master the basic principles of science to understand plant life adequately. This interest in botany remained throughout his life and surfaced in his later work. Almost immediately, he transferred to Darmstadt after his father was appointed to a teaching position there. Staudinger pursued advanced studies at Munich (briefly) and at Halle, where he wrote his dissertation on the malonic esters of unsaturated compounds under the direction of Daniel Vorlander. He received his Ph.D. in organic chemistry on August 3, 1903.

Staudinger continued his research at the University of Strasbourg to obtain his teaching qualification, which he received in 1907. It was at Strasbourg, working under Johannes Thiele, that Staudinger made his first important discovery, the ketene, a highly reactive unsaturated form of ketone. Having earned his teaching qualification, he became an assistant professor at the Technische Hochschule in Karlsruhe, where he remained until 1912, when he succeeded Nobel laureate Richard Willstätter at the Eidgenossische Technische Hochschule in Zurich. Because of the shortages of World War I, Staudinger’s work at Karlsruhe and Zurich kept very much in touch with the needs of industry and Germany. Staudinger worked on the synthesis of rubber and, with his student, Leopold Ružička, studied the composition of the insecticide pyrethrin and developed an artificial pepper. With the help of another student, Tadeusz Reichstein, Staudinger succeeded in synthesizing the aroma of coffee, a commodity cut off from wartime Germany. However, Staudinger’s main thrust of research during these early years remained the study of ketenes, about which he published Die Ketene(1912), a book that is still considered a standard. In 1926, Staudinger left Zurich to accept a position as a lecturer of chemistry at the University of Freiburg im Breisgau, where he remained until his retirement in 1951.

In 1927, Staudinger married Magda Woit, a Latvian plant physiologist, with whom he coauthored many papers. They had no children.

Life’s Work

Staudinger, who was an educator, author, inventor, and researcher, made his greatest contribution to science by enunciating and proving the macromolecular theory, which states that rubber, plastics, and similar substances (polymers) are composed of long chain molecules having hundreds of repeating units connected by primary covalent bonds. For these molecules, which can have indefinitely large molecular weights, Staudinger coined the term “macromolecule.”

Prior to 1920, the relatively insoluble, uncharacterizable resinous substances that organic chemists frequently found on the bottom of their reaction flasks were an enigma, although they were suspected to be polymeric (having chains composed of repeating units) in nature. This group of substances, of which rubber is a member, displays a nonlinear relationship between viscosity and concentration, nonstoichiometry, an inability to crystallize and in general a failure to adhere to the same physical laws as conventional molecules.

There were two prevailing theories at the time, the most popular of which was the micellar theory of the German chemist Carl Harries, who believed that these substances were physical aggregates of low-molecular-weight polymers held together by weak residual forces, and the theory of Samuel Pickles, who believed that the substances were composed of long chain molecules held together by primary chemical bonds. In 1910, while working under Carl Engler at Karlsruhe, Staudinger discovered a new way to synthesize isoprene, the structural unit of synthetic rubber, and was thereby introduced to this controversy. Harries thought that the weak secondary forces that held the isoprene rings of rubber together arose from their unsaturated double bonds, so Staudinger devised an experiment to test this theory. Harries predicted that removal of the double bonds by hydrogenation would restore the native, conventional properties of these molecules, causing them to form liquid hydrocarbons, but a series of experiments carried out in 1922 by Staudinger gave no such results. Staudinger’s saturated synthetic hydrorubbers were nondistillable, colloidal, and differed little from natural rubber. It was this experiment that caused him to embark on an ambitious new area of research to prove his macromolecular theory.

In an attempt to avoid the experimental difficulties associated with natural polymers, Staudinger, in the early 1920’s, chose to extend his studies to the polymers of styrene and oxymethylene (the solid form of the preservative formalin), synthetic models of rubber and cellulose, respectively. The physical properties of the homologous series of paraffin waxes, long chain hydrocarbons having the general formula C n H2 n +2, vary with chain length. Staudinger, recognizing that styrene behaves in a similar manner to these paraffins, came to the conclusion that polystyrene is also one member of a homologous series, the properties of which depend on the average chain length.

This inspiration led Staudinger to engage in a series of experiments to measure the viscosity of polymers, a technique well established as being sensitive to the molecular weight of small molecules. In this work, Staudinger indeed found a direct correlation between the viscosity and the length of the polystyrene samples from which he was able to calculate the molecular weight of the polymer molecule. The results indicated an extremely large chain, which was presented as strong evidence for his macromolecular concept. This work, as well as his hydrogenation experiments, were published in his classic book Die hochmolekularen organischen Verbindungen, Kautschuk und Cellulose (1932; the high-molecular organic compounds, rubber, and cellulose).

Staudinger presented his results on three important occasions from 1924 to 1926, but they were not well received. Especially the last two times, at the meeting of the Zurich Chemical Society and the Düsseldorf meeting of the Association of German Natural Scientists and Physicians, Staudinger encountered vigorous opposition from the proponents of the micellar aggregate theory. In fact, Staudinger once stated that he only convinced one person at the Düsseldorf meeting, Richard Willstätter. They did not believe that Staudinger’s viscosity measurements were a reliable indicator of molecular weight but thought rather that his results reflected a state of aggregation of numerous molecules. Furthermore, the well-respected mineralogist Paul Niggli insisted that a molecule with dimensions larger than the unit cell obtained by X-ray diffraction could not exist. The scientific community would not be convinced of the existence of macromolecules unless they could be sure that Staudinger was looking at a pure sample instead of an aggregate of many molecules.

At this point, some events began to turn in Staudinger’s favor. Toward the end of the 1920’s, Theodor Svedberg and Robin F†hraeus conducted experiments to measure the equilibrium sedimentation of oxyhemoglobin and carbonylhemoglobin using an ultracentrifuge, a powerful new tool for determining molecular weights. From these experiments, hemoglobin was found to have a very high molecular weight of about sixty-five thousand, four times higher than that given from elementary analysis. Furthermore, this was a sharply defined molecular weight, without the spread that would be expected if hemoglobin were an aggregate. The recognition of a high-molecular-weight compound in protein chemistry by an independent method lent welcome support to Staudinger’s macromolecular theory.

Staudinger hoped to measure the molecular weight of synthetic and natural polymers by this method, so he applied for a grant to purchase an ultracentrifuge for Freiburg. His grant was turned down, however, a reminder of the skepticism Staudinger and his concepts endured. In a fit of depression over this event, Staudinger turned again to viscosity measurements and in 1929, working with two students, R. Nodzu and E. Ochiai, he showed that for linear molecules the viscosity of their solutions is proportional to the number of residues in the chain. This relationship between the specific viscosity and the molecular weight is known as Staudinger’s law and is widely used in industry wherever there is polymer research in progress.

Finally, other evidence emerged to support the existence of macromolecules. Flow birefringence experiments conducted by R. Signer showed that polymers in solution had very large length to breadth ratios; the American chemist W. H. Carothers succeeded in synthesizing nylon by a condensation polymerization reaction that liberated an amount of water equal to the number of residues in the product; and X-ray crystallographers at last realized that a molecule could be larger than the unit cell. With this work accomplished, Staudinger was finally able to concentrate on his first love, biology, for which he had been preparing himself for thirty years.

Staudinger’s youthful interest in biology emerged in 1926, when he began studies on the structure and function of macromolecular compounds in living systems. At a lecture delivered in Munich in 1936, Staudinger stated, “Every gene macromolecule possesses a quite definite structural plan, which determines its function in life.” This statement was perceptive in the light of the fact that the genetic code was not understood until 1953. Some of Staudinger’s ideas in biology were simplistic, however, and he clearly lacked a strong understanding of biological concepts. For example, he took the macromolecular concept to an extreme when he calculated the molecular weight of a bacterium. In 1947, Staudinger published Makromolekulare Chemie und Biologie, which gives his view of future developments in molecular biology.

With the help of his wife, Magda, Staudinger spent the last part of his career working on biologically related topics and using the phase-contrast microscope to visualize macromolecules. This work ended when Freiburg was bombed in 1944 during World War II. Staudinger’s energies had been spent by this time and he retired in 1951. Staudinger died of a heart condition at the age of eighty-four.

Significance

By the time Staudinger began his work on macromolecules, he was already forty and had a considerable reputation as an organic chemist. Indeed, his colleagues could not understand why one of his stature would want to do research in an area they called “grease chemistry.” It is fortunate, however, that Staudinger did take up the challenge, for a less persistent, less eloquent, or less respected chemist could not have endured the attacks and controversy surrounding the macromolecular theory. Unfortunately, there was even conflict among the supporters of the macromolecular theory. Herman Mark and Frederick Eirich believed that polymers could be flexible chains and form micellelike bundles while still being macromolecules, a view that proved to be correct, but Staudinger rejected the micellar theory so completely that he believed that macromolecules could be nothing but rigid rods. Because of this controversy, Staudinger was not awarded the Nobel Prize until 1953.

Staudinger was a prolific writer, having published more than five hundred papers and books. He also founded and became the editor of the journal Die Makromolekulare Chemie in 1947. Staudinger was the founder of macromolecular chemistry, and his work laid the foundation for a tremendous polymer industry. In addition, his students and disciples formed the core of this area of research. Besides the Nobel Prize, Staudinger won many other prizes for scientific achievement as well as two honorary degrees.

Although best remembered for his pioneering work in polymer chemistry, Staudinger was also a first-rate teacher and administrator. Students came from all over the world to work under him; he was so successful at inspiring in others his talent for creative thinking that two of his students, L. Ružička and T. Reichstein, each won the Nobel Prize. His students remember him as a quiet man who was fond of explosions.

Bibliography

Furukawa, Yasu. “Staudinger, Carothers, and the Emergence of Macromolecular Chemistry.” Ann Arbor: University Microfilms International, 1983. A dissertation by Furukawa for his doctorate in the history of science. Describes in detail Staudinger’s education and work and puts them into their proper historical perspective. References are included.

Meikle, Jeffrey L. American Plastic: A Cultural History. New Brunswick, N.J.: Rutgers University Press, 1995. An interdisciplinary cultural history of plastics, written by an art historian and professor of American studies. Explores plastics in the context of invention and technology, material culture studies, advertising and marketing, industrial design, consumerism, and cultural history. Recommended especially for those seeking a nontechnical study of the effects of Staudinger’s work beyond the sciences.

Morawetz, Herbert. Polymers: The Origins and Growth of a Science. New York: Wiley-Interscience, 1985. The publication of this book was suggested by Staudinger’s wife, Magda. The chapter “Staudinger’s Struggle for Macromolecules” gives the best step-by-step account of the battle to prove the macromolecular theory.

Olby, Robert. “The Macromolecular Concept and the Origins of Molecular Biology.” Journal of Chemical Education 47 (1970): 168-174. A lucid account of the intellectual battles fought in the effort to establish the macromolecular concept in the field of molecular biology.

Quarles, Willem. “Hermann Staudinger: Thirty Years of Macromolecules.” Journal of Chemical Education 28 (1951): 120-122. A summary of Staudinger’s life’s work, written in honor of his seventieth birthday. The article emphasizes Staudinger’s early years. It describes his manner, teaching accomplishments, and his relationship with his students, some of whom became Nobel laureates. A portrait is included.

Staudinger, Hermann. From Organic Chemistry to Macromolecules. New York: Wiley-Interscience, 1970. An autobiography based heavily on Staudinger’s scientific publications. This book has the best account of Staudinger’s early work and explains the motivations for his choice of research projects. Explains Staudinger’s line of reasoning and why he was convinced that his macromolecular concept was correct. Contains almost all the references to his scientific publications as well as portraits of him and of some of the people he admired.

Yarnell, Amanda. “Ketenes Turn One Hundred.” Chemical and Engineering News 84, no. 2 (January 9, 2006): 46. Reports on a gathering of chemists commemorating the centennial of Staudinger’s discovery of ketenes. Discusses his research and subsequent developments in ketene chemistry.