Eugene Pashkovski - Fellow, Elected 2026

Eugene Pashkovski is one of those very rare individuals who is able to successfully straddle the academic/industrial divide – and manages to make important contributions on both sides of the fence. He is an ambassador for the Lubrizol Corporation (well-known to a whole generation of rheologists as a supplier of Carbopol “model” yield stress fluids), as well as an experienced industrial rheologist. Over the past decade he has employed various shear and extensional rheometers to correlate rheological properties of engine oils with fuel economy increase (FEI). He developed tribological models using the Oldroyd-B and Giesekus constitutive models to explain the role of engine oil viscoelasticity in FEI that increased with the Trouton ratio of oils due to reduction of viscous energy losses in the hydrodynamic lubrication regime. Eugene’s work fundamentally shifted the perspective of polymers from merely being viscosity modifiers to performance polymers being a critical element of modern engine lubricant formulations.

As the hydraulic fluid efficiency was associated with linear poly(ethylene)-co-(propylene) (OCP), it was essential to explain the mechanism by which this product provided energy savings of 3-8%. Viscosity measurements and accompanying theoretical analyses using the FENE and PTT models verified that the viscoelastic effects tend to reduce the magnitude of the secondary flow pattern, commonly known as the Dean-vortex regime, which arises in curved geometries, by an average of 15% compared to the base liquid.

By performing time-resolved mechanical spectroscopy on oil-based colloidal gels, Eugene and his team have also quantified the gelation behavior and provided a physical explanation for the temporal evolution of the viscoelastic properties of an important class of Marine Diesel Cylinder Lubricants (MDCLs). The collapse of viscoelastic spectra, onto a master curve that spans over ten orders of magnitude in frequency helped to compactly capture the rheological behavior of these materials using a Fractional Zener model, accurately measuring the temporal evolution of viscoelastic properties through the gelation with high temporal resolution. The application of optimized windowed chirps was used to predict the lifetime of these marine lubricants and improve the stability of these products.

Eugene and his team have also investigated the effect of breaking and reptation times of micelles on the linear and non-linear rheology of viscoelastic mixed anionic-zwitterionic surfactant solutions. It was demonstrated that the value of the breaking time ${\tau }_{break}$ (rather than the Maxwellian relaxation time) controls a metastable branch on the stress-rate diagram. Transient flow responses corroborated the quasi-static flow findings and further revealed the significance of microscopic dynamic parameters on flow behavior. In work with Dave Weitz and Luca Cipelletti, he has contributed to the understanding of slow dynamics in soft glassy materials (SGM), including compressed emulsions and biopolymer microgels, using camera-based diffusion wave spectroscopy and multi-speckle dynamic light scattering, combined with a series of creep experiments to understand the effect of aging on slow dynamics.

He is a regular attendee at SOR meetings, serving as a Keynote Speaker, lead author of a technical article in the Rheology Bulletin, speaker and mentor at the Industrial Rheology Lunch and a Judge at the Future of Rheology session also.