Elmer Otto Kraemer (1898–1943) was a pivotal figure in the evolution of physical chemistry, specifically in the transition from classical colloid science to modern polymer physics. Though his life was cut short at the height of his productivity, his work at the DuPont Experimental Station and his collaboration with Nobel laureate The Svedberg helped lay the quantitative foundation for how we understand large molecules—the building blocks of everything from biological proteins to synthetic plastics.
1. Biography: From the Midwest to the Frontiers of Science
Elmer Kraemer was born on February 27, 1898, in Liberty, Wisconsin. He showed early promise in the sciences, enrolling at the University of Wisconsin-Madison, where he earned his B.S. in 1918. After a brief stint in industry and service during the tail end of WWI, he returned to Wisconsin for graduate studies under J. Howard Mathews, receiving his Ph.D. in 1924.
The defining moment of Kraemer’s early career came immediately after his doctorate. He was awarded an American-Scandinavian Foundation fellowship to study at Uppsala University in Sweden. There, he worked in the laboratory of The Svedberg, who was then perfecting the ultracentrifuge—a device that would revolutionize the study of macromolecules.
Upon returning to the U.S., Kraemer briefly served as an assistant professor at the University of Wisconsin. However, the burgeoning industrial research scene beckoned. In 1927, he joined the DuPont Company’s Experimental Station in Wilmington, Delaware. At DuPont, he became a lead scientist in the Fundamental Research Group, working alongside other legends of chemistry to bridge the gap between theoretical physics and industrial application.
2. Major Contributions: Measuring the "Giant Molecule"
Kraemer’s work was characterized by a drive for precision. Before the 1930s, the existence of "macromolecules" (very large molecules) was a subject of intense debate. Kraemer provided the mathematical and experimental proof needed to settle the argument.
- The Ultracentrifuge in America: Kraemer was responsible for bringing the Svedberg ultracentrifuge technology to the United States. He recognized that by spinning solutions at incredibly high speeds, one could observe how fast particles settled (sedimentation), allowing for the direct calculation of molecular weights.
- The Kraemer Equation: In the study of polymers, "intrinsic viscosity" is a measure of a solute's contribution to the viscosity of a solution. Kraemer developed a mathematical relationship (often paired with the Huggins equation) to determine this value. The Kraemer Equation remains a staple in polymer science textbooks:
ln(ηrel) / c = [η] + k'' [η]2 c
This allowed scientists to characterize the size and shape of polymers using relatively simple laboratory equipment. - Molecular Weight Distribution: Kraemer was among the first to emphasize that synthetic polymers are "polydisperse"—meaning a sample of plastic isn't made of identical molecules, but a distribution of different lengths. He developed methods to calculate these distributions, which is critical for controlling the physical properties of materials like rubber and nylon.
3. Notable Publications
Kraemer was a prolific writer and editor who sought to codify the scattered knowledge of colloid science.
- "The determination of the size and weight of colloidal particles" (1924): His early foundational work on sedimentation.
- "Molecular Weights of Cellulose and Cellulose Derivatives" (1933): A landmark paper that applied physical chemistry to natural polymers, proving they were true macromolecules.
- "Intrinsic Viscosity" (1938): Published in Industrial & Engineering Chemistry, this paper introduced the Kraemer Equation and standardized the nomenclature for viscosity in polymer science.
- Advances in Colloid Science (Editor, 1942): Kraemer served as the founding editor of this influential series, which helped define the field for the next generation.
4. Awards & Recognition
While Kraemer did not live long enough to receive the "lifetime achievement" awards often granted to senior statesmen of science, he was highly decorated within the American chemical community:
- Franklin Institute Membership: He was an active and respected member of the Franklin Institute, contributing to their scientific committees.
- American Chemical Society (ACS) Leadership: He held various leadership roles within the Colloid Division of the ACS.
- The Svedberg’s Peer: Perhaps his greatest "award" was the professional respect of The Svedberg, who viewed Kraemer not just as a former student, but as the primary authority on ultracentrifugation in the Western Hemisphere.
5. Impact & Legacy
Kraemer’s legacy is woven into the fabric of modern materials science. By providing the tools to measure molecular weight accurately, he enabled the "Polymer Revolution."
Without Kraemer’s analytical methods, the development of synthetic fibers would have been a matter of guesswork. His work allowed chemists to understand why one batch of polymer was brittle while another was flexible. Today, the "Kraemer Plot" is still used by rheologists and polymer chemists worldwide to characterize new materials, from drug-delivery hydrogels to high-performance aerospace composites.
6. Collaborations: The DuPont Powerhouse
Kraemer worked at DuPont during its "Golden Era," and his collaborations were world-class:
- Wallace Carothers: Kraemer provided the physical-chemical measurements that supported Carothers’ synthetic work. While Carothers was inventing Nylon and Neoprene, Kraemer was the one proving exactly how large and heavy those new molecules were.
- William Lansing: Together, Kraemer and Lansing refined the mathematics of "weight-average" versus "number-average" molecular weights, a distinction that is fundamental to polymer science today.
- The Svedberg: Their lifelong correspondence ensured that Swedish innovations in physics were immediately applied to American industrial chemistry.
7. Lesser-Known Facts
- The Microscopy Expert: Beyond the ultracentrifuge, Kraemer was a pioneer in ultramicroscopy. He developed techniques to see particles that were previously invisible under standard light microscopes, using light scattering to pinpoint their locations.
- A Sudden End: Kraemer’s career ended tragically and abruptly. He died of a cerebral hemorrhage in 1943 at the age of only 45. At the time of his death, he was working on critical research related to the war effort, specifically regarding synthetic rubber—a vital commodity after natural rubber supplies were cut off during WWII.
- Defining "Intrinsic Viscosity": Before Kraemer, the terminology for how thick a liquid becomes when you add polymers was a mess of conflicting definitions. Kraemer is largely responsible for the standardized terms (like inherent viscosity) that chemists use today to ensure they are all speaking the same language.
Elmer Kraemer was the "metrologist" of the macromolecular world. He took the abstract idea of giant molecules and gave scientists the ruler and scale to measure them, turning a speculative theory into a rigorous, predictable science.