Dr. Donald R. Paul
On September 1, 1967, Professor Donald R. Paul joined the faculty of The University of Texas at Austin. To commemorate his 50th anniversary as a faculty member, a celebration and symposium will be held in his honor this fall in Austin, October 12 through 14.
Paul is a legend in the field of polymer engineering and science, with a strong focus on fundamental membrane science, based not only on the quantity of contributions to the field but also for the profound quality and insight that he has brought to the field. Paul is among the most cited scientists in the world. His work in polymer engineering and science has been cited more than 42,000 times according to Web of Science and his h-index is 100. Many of the citations are to papers that are classics in their field. As a result of making some of the key discoveries in several areas of polymer science and technology, Paul has received virtually every possible award and honor in the field of polymer and membrane science, including election to the National Academy of Engineering, receipt of the Alan S. Michaels Award for Innovation in Membrane Science and Technology from the North American Membrane Society, receipt of the Herman F. Mark Polymer Chemistry Award, the Applied Polymer Science Award, and the E.V. Murphree Award from the American Chemical Society, and receipt of the William H. Walker Award from the American Institute of Chemical Engineering. He has been elected as a Fellow of the American Institute of Chemical Engineers, the Society of Plastics Engineers, the Materials Research Society, and the American Chemical Society (plus the Divisions of Polymeric Materials; Science and Engineering and Polymer Chemistry).
Today, it is well recognized that the mechanism by which small gas molecules migrate through polymer membranes is via the so-called solution-diffusion mechanism wherein gas molecules first dissolve into the high-pressure face of a membrane, then diffuse down the concentration gradient, and then desorb from the downstream face. This is also the mechanism by which liquids are transported through membranes such as reverse osmosis desalination membranes. In the early 1970s, there was great controversy in the field of membrane science about whether small molecule transport occurred through polymers via solution-diffusion or flow through unobservably small pores in polymers. Paul undertook a series of elegant, fundamental studies that clearly demonstrated the validity of the solution-diffusion approach. Practically single-handedly, he convinced an entire generation of scientists and engineers of the fundamental transport mechanism of small molecules in polymers. It is difficult to describe the enormity of this contribution.
Polymers used today in membrane applications such as air separation, hydrogen purification, and natural gas purification are typically rigid, glassy polymers. Paul conducted critically important systematic studies in the ’70s and ’80s on the gas separation properties of polymers that later went on to provide the fundamental framework and understanding upon which today’s commercial membranes are based. The permeation properties of glassy polymers show a very distinct dependence on pressure, with permeability decreasing as pressure increases. Professor Paul, together with a former Ph.D. student, Bill Koros, formulated the most widely-used model to describe the permeability decrease with increasing gas pressure in glassy polymers, the dual mode model. This model has become the de facto standard in the field of gas separation membranes and has been used by countless researchers the world over to describe and correlate their experimental permeability data.
Paul is highly cited for his work in polymer blend thermodynamics. Before his work, it was widely believed that almost any pair of polymers would be immiscible. It was further believed that it would be virtually impossible to prepare blends of polymers that would be miscible at a molecular scale. Paul questioned this conventional wisdom and did systematic experimental studies delineating the molecular basis for polymer blends that are miscible with one another at a molecular level. In addition to performing elegant experimental studies that unmistakably demonstrated the miscibility of appropriately selected polymers, Don developed a widely-used theory describing miscibility of polymer blends. He edited several important books on this topic, and his work in this area has formed the basis for the industrial practice of using miscible polymer blends for wide variety of structural and other applications as well as the theoretical basis underpinning much of the modern literature in this area. In addition, he popularized the concept of “compatibilization” of multiphase blends using block and graft copolymers and made significant contributions to rubber toughening using “reactive compatibilization.” He co-edited a two-volume book with S. Newman in 1978 and another two-volume set with C. B. Bucknall in 2000 that have become classics in the field of polymer blends with translations into Chinese and Russian.
Paul made key contributions to fundamental understanding of relaxation of glassy polymers at nanometer length scales that are important, from a practical prospective, in the design and operation of gas separation membranes and, from a fundamental perspective, important for understanding the behavior of nanoconfined polymers. His work in this area, directed towards understanding and describing physical aging in extremely thin glassy films, has utilized state-of-the-art depth-resolved positron annihilation studies combined with other techniques to make the first measurements of physical aging, probed by gas permeability, in polymer films less than 20 nanometers thick [Polymer, 51, 3784-3792 (2010); Polymer, 50, 6149-6156 (2009); Polymer, 50, 5565-5575 (2009)]. He continues to actively pursue new research areas, including recent studies aimed at laying a fundamental framework to understand ion sorption, diffusion, permeation and conductivity in charged polymers used in electrodialysis and other applications [e.g., ACS Applied Materials & Interfaces, 9(4), 4044-4056 (2017), Physical Chemistry Chemical Physics, 18, 6021-6031 (2016)].
Paul has provided outstanding service to the polymer and membrane communities for many years. He was involved with the North American Membrane Society and the Journal of Membrane Science practically from their inception. He was editor of Industrial and Engineering Chemistry Research for more than 25 years, which is the record for the longest serving editor of this journal. He has served on countless other editorial boards, professional society committees and other service/advisory positions both in the US and abroad, sharing his wisdom and insight broadly.