Ralph H. Colby received his B.S in Materials Science and Engineering from Cornell University in 1979. He worked for 2 years at the General Electric Company in rheology and
process development before enrolling as a graduate student at Northwestern University’s Chemical Engineering Department. He received a M.S in 1983 and a Ph.D. in 1985 under
the guidance of William W. Graessley. Ralph’s thesis work involved a detailed study of the rheology of linear polybutadiene melts and was carried out in part at the Corporate
Research & Science Laboratories of Exxon Research and Engineering Company, where he spent 15 months as a visiting student. Ralph’s thesis papers are considered to be classic.
He still holds the record for having measured the viscosity of the monodisperse polymer melt with the largest number of entanglements (more than 8000). After graduating from
Northwestern, Ralph moved to Rochester, NY and worked for ten years at the Kodak Research Laboratories where he developed a highly successful research program on experimental
rheology of soft matter. Colby’s areas of interest over these ten years included linear polymer melts and solutions, miscible polymer blends, block copolymers, randomly branched
polymers, polymer gels, liquid crystalline polymers, polyelectrolytes, proteins, surfactants, and colloidal suspensions. He initiated collaboration with world-class theorist
Michael Rubinstein. This is one of the most successful and productive collaborations in our field, which still continues today. One of the most important outcomes of this
collaboration is the outstanding Polymer Physics textbook (Oxford, 2003), probably the best of its kind; it is a masterpiece of clarity and profoundness, and includes an amazing
collection of problems of varying difficulty. In 1995 Colby moved to academia joining the faculty of the Pennsylvania State University, where he has been Professor of Materials
Science and Engineering since 2000. Ralph received the C. E. K. Mees Award of Eastman Kodak Company (1987) and the Wilson Research Award of Penn State (2004). He served as
co-chair of the Technical Program of the XVth International Congress on Rheology and co-editor of its proceedings (AIP, 2008). He is a fellow of the American Physical Society
and the editor of the Journal of Rheology.
From the beginning of his research career Ralph followed the legacy of Bill Graessley and recognized that the synergy of synthesis, properly designed and carefully executed
experiment, and deep understanding of theory is necessary for advancing the field of molecular rheology. This synergy of expertise remains the cornerstone of Ralph’s approach
to research in a wide range of topics in soft matter, and is behind his huge success. In fact, Ralph has a well-deserved reputation as one of the best rheological experimentalists
in the world. At the same time, he has an extraordinarily deep grasp of theory and his integrated approach combining experiments and theory results in contributions with the
broadest possible impact.
In 1988, Ralph discovered a remarkable property of miscible polymer blends: the contributions of individual components to viscoelastic response have temperature dependences relative
to the glass transition temperature (Tg) for the blend that closely match those of the pure components relative to their own individual Tg’s. Thus, the dynamics
of miscible blends follow fundamentally different temperature dependencies from those of polymer solutions and can exhibit thermorheological complexity. Colby’s observations attracted
many groups to examine different blends in order to test the generality and to search for molecular explanations of this phenomenon. Ralph’s subsequent work in collaboration first with
Gerry Fuller and later with his long-time colleague, Sanat Kumar, has brought to the subject a variety of new spectroscopic probes and molecular simulations.
Colby has laid the groundwork for our current understanding of constraint-release effects in entangled polymers in a series of classic works including his papers with Rubinstein and
later with Viovy explaining the interplay of reptation, contour length fluctuations and constraint release in bidisperse polymers. These works are still the state of the art in the
field today, providing the ingredients in most modern tube models of polymer relaxation. Moreover, the “Colby-Rubinstein” theory for semi-dilute solutions of polymers in theta solvents
established the “4/3 exponent” for entanglement spacing as a function of concentration, and is commonly used not only for predictions of solution rheology, but also for the state of
the art theories of “dynamic dilution” for the rheology of branched polymer melts.
Ralph has made several experimental and theoretical (with Dobrynin and Rubinstein) breakthroughs that shaped the field of polyelectrolyte rheology. These breakthroughs include the
increased relaxation time and the appearance of shear thinning at lower shear rates as the solution concentration is lowered, the observation and the explanation of the fact that
the semidulute unentangled regime spans 3 decades in concentration, whereas the entangled regime is qualitatively different from that of uncharged polymers. He has also extended
his work to ionomers. The sticky reptation model with Leibler and Rubinstein and the association of loss modulus peak in the rubbery plateau region of ionomers to ionic domain
relaxation, brought new life to the field. Currently, Colby’s group is revisiting outstanding fundamental problems such as ionic mobility, ion aggregate structure at different
length scales and glassy and chain dynamics by combining rheology with dielectric spectroscopy, SAXS, and scaling theory. This poorly understood class of materials is expected
to become very important for many applications including actuators, sensors, separators between the electrodes of advanced batteries, and fuel cell membranes.
Using their landmark classification of gelation, based on the overlap parameter and related number of entanglements between crosslinks, Colby and co-workers developed models for
the rheology of randomly branched polymers near the gel point and showed their universality. This discovery has implications to the design and synthesis of different types of
branched polymers. Ralph applied his expertise on gelation of simple flexible polymers to more complex systems, such as denaturated collagen in order to understand the kinetics
of helix formation. Using rheo-optics he showed that optical rotation is proportional to the number density of helices. The latter were measured simultaneously with viscosity
and shear modulus. Rheological and scattering investigations of the two main constituents of synovial fluid, hyaluronic acid and the globular plasma proteins (that consist
primarily of serum albumin and gamma-globulins) showed why synovial fluid is such a great lubricant for mammalian joints. This key discovery lead to understanding the lubricating
action of this fluid, with implications to medicine, pharmaceutical science, and bioengineering.
Perhaps the single most important outstanding issue in the field of glass formation is whether there is a length scale associated with dynamic heterogeneities and how it depends
on temperature. Here again, the contribution of Colby has had a huge impact. Using a dynamic scaling model, he has demonstrated that the length scale of cooperative motion of all
glass-forming liquids follows universal temperature dependence. In the same context, the relaxation times of a particular glass former are expressed as the product of the universal
cooperative length scale raised to the sixth power and a function related to non-universal thermally activated process. Well above glass transition temperature, a crossover to
Arrhenius temperature dependence is recovered and provides an estimate of the caging temperature. This very important discovery offers ways of critically testing universalities in
the behavior of glass-formers, which represents one of the most important challenges.
Copolymers, liquid crystalline polymers and surfactant micelles are three popular classes of structured polymeric materials. Ralph realized early on that in order to understand these
complex fluids one needs to study their structure and dynamics on scales much larger than their molecular dimensions. Achieving this understanding required careful and patient
measurements of rheology down to extremely low rates in combination with application of structure probing techniques. Colby’s classic paper on a block copolymer with shear viscosity
measurements down to unprecedented shear rates of 10–7 s–1 proves his dedication, determination to tackle, and ability to solve challenging problems. His
collaboration with Bates and Tirrell has opened the route for a large body of works on shear-alignment of block copolymer micelles.
Ralph’s current projects include studies of ionomers, branched polymers, and nanocomposites. We are anxiously awaiting the new discoveries from Colby’s lab.
The above brief description is a testimony to Ralph’s remarkable instinct for important and timely problems that attract the attention of both scientific and industrial communities.
Colby is also one of the pioneers responsible for the transformation of rheology into a molecular and structural science, drawing in complementary experimental techniques such as
scattering (X-ray, neutron, and light), dielectric spectroscopy, polarimetry, NMR, and microscopy, as well as molecular simulations, in order to cover all the essential structural
timescales and lengthscales in complex fluids. In addition, he has a rare talent in selecting strategic and long-lasting collaborations with top-notch scientists.
The great success of the International Congress on Rheology in Monterey is, to a large extent, due to Ralph who, along with Gary Leal, put together a memorable program. Ralph is
always encouraging, helpful, and generous with his time. He is constantly demonstrating scholarship and leadership in taking rheology into new territories, where it can play a crucial
role in solving major scientific and technological problems.
Ralph is a devoted father of Melissa, Edwin and Graham. He enjoys playing ice hockey and is a passionate fan of the Boston Red Sox. If you cannot go with Ralph to a football game of
the Nittany Lions at State College, make sure that you dine with him. You will enjoy his unique humor, but do not compete with him on after-dinner drinks! Cordial congratulations to
Ralph on receiving the 2012 Bingham medal!