Giuseppe (Pino) Marrucci was born on April 16, 1937 in Italy. He completed his higher education at the University of Naples, graduating with his Chemical Engineering Ph.D. in 1961.
He remained at the University following graduation, serving as Assistant to the Chair of Industrial Chemistry and working his way into an Associate Professor of Chemical Engineering
position (1965). Marrucci accepted a position as Chair of Principles of Chemical Engineering at the University of Palermo in 1970. He returned to the University of Naples in 1976,
accepting chair positions in Non-Newtonian Fluid Mechanics as well as Thermodynamics. Marrucci remained at the University of Naples for the remainder of his career, strengthening
its reputation and activity as a destination for rheology. His four main areas of research are discussed below.
Entangled Polymers. Since the introduction of the seminal Doi-Edwards theory in 1978, the two most important advances to this theory for the rheology of flexible-chain
polymers have been due to Marrucci and coworkers. The first advance, in the early 1980's was the addition of “chain stretch” to the basic equations. Chain stretch permits overshoots
in normal stresses to be predicted. This improvement did not, however, cure the most severe, and well-known, deficiency of the famous Doi-Edwards theory, which predicts excessive
shear-thinning (and ultimately shear-banding). Recently, however, Marrucci introduced the concept of “convective constraint release” (CCR), which repairs this final, major, problem
in tube models for fast flows of linear polymers. Marrucci's “convective constraint release” concept led to a flurry of activity and rejuvenated this field. After the original
development of the Doi-Edwards equation, this contribution is probably the most important idea in the entire field of tube-based constitutive equations for melts of flexible polymers.
Marrucci also made numerous other contributions to our understanding of the rheology of entangled melts. These include his invention of the concept of “dynamic dilution"”in the early
1980's, which was applied to star polymers by Ball and McLeish in 1989. This, along with primitive path fluctuations (introduced by de Gennes), is the key concept required to understand
the rheology of branched polymers. “Another very recent contribution is the idea of a “local force balance” between entangled polymer molecules; this concept seems to be the key to
performing some dynamic simulations of entanglement networks and may be responsible for controlling the magnitude of the second normal stress difference.
Liquid Crystals and Liquid Crystalline Polymers. In 1989, Marrucci and Maffetone explained the cause of the mysterious negative first normal stress difference in shearing
flows of nematic polymers. The explanation involved director tumbling, by which shearing flows actually cause the molecules to be less aligned than in the absence of shear, producing a
reactive force that is opposed to the shearing direction, giving rise to a negative N1. This solution required a deep understanding of the dynamics of liquid crystalline
polymers, and combined with their numerical solution to the Smoluchowski equations for the distribution function for liquid crystal orientations, produced a convincing prediction and
explanation of negative normal stress differences.
In the early 1990’s, Marrucci and Greco developed a theory for the structure of a defect core that can be applied to flowing liquid crystals. When combined with the “Doi theory” for
nematic polymers, this theory allowed the development of numerical solutions for the director field in flowing liquid crystals, and it has subsequently been widely used. Marrucci made
many other contributions to liquid crystal flow, including the widely-cited “Marrucci scaling law” for the density of disclinations as a function of shear rate, estimates of the magnitudes
of viscous stresses in flowing liquid crystalline polymers, a “nematic dumbbell” model that explains why nematics with flexible spacers do not show director tumbling, and a theory for the
effect of polydispersity on the rheology of concentrated rod-like polymers.
Constitutive Equations and non-Newtonian Fluid Mechanics. In addition to the above-cited contributions to the molecular physics of rheology, Marrucci has never lost sight
of the importance of rheology as an engineering discipline. Marrucci has produced numerous simplified constitutive equations, useful for calculating the stresses in complex flows. These
equations include a simplified differential version of the Doi-Edwards equation, equations that improve the normal stress predictions of that equation, equations for liquid crystalline
polymers, associating polymers, and others. Not to be overlooked are Marrucci’s collaborations with Mort Denn (1986 Bingham Medalist), which include analyses of filament breakup and of
the rheology of suspensions. In the 1970's, Astarita and Marrucci contributed a wonderful book on rheology, perhaps the most lucid work on the subject available at the time.
Dilute Polymer Solutions. In a 1970’s paper, far ahead of it its time, Marrucci and coworkers used molecular simulations to discover the importance of folded conformations
in the extensional flow of dilute polymer solutions. The simulations were rather primitive compared to those now possible, but Marrucci must be acknowledged as the first to observe these
conformations, whose significance only became apparent as a result of the DNA imaging work of Steve Chu and coworkers. Also, early in his career, Marrucci contributed an expression for the
free energy of a deformed polymer chain that has since become a mainstay of polymer thermodynamic analyses.
Marrucci’s service to rheology extends well beyond his scientific contributions. He has regularly hosted or co-hosted rheology meetings, including three meetings on the island of Capri near
his beloved University of Naples and the International Congress on Rheology in Naples. He is a wonderfully clear communicator and a spirited participant in the international community of
rheologists whose contributions are always marked by a rare combination of intelligence and grace.
Tanner, R. I.; Walters, K. “4.16 Giuseppe Marrucci.” Rheology: an historical perspective; Elsevier: Amsterdam, 1998.
Note: This biography is an adaptation of the following article previously published by The Society of Rheology.
2003 Bingham Award Goes to Guiseppe Marrucci. Rheology Bulletin 2003, 72(2).