Speaker: Prof. Masao Doi (土井正男教授)

Time: 15:00-16:00, 25 February 2022 (Friday) (Beijing time)

Venue: T2-102


The Onsager principle is a variational principle proposed by Lars Onsager in 1931 in his celebrated paper on the reciprocal relation in non-equilibrium thermodynamics. The principle is important in the physics of polymer and soft matter. Almost all kinetic equations which have been used to describe the dynamics of polymer and soft matter systems are derived from this principle. The Onsager principle is also useful in solving these equations. Since it is a principle of minimization, it can be used to get approximate solutions of the equations. Here I review the principle from an application point of view. I take examples from capillary hydrodynamics, gel dynamics and flow of viscoelastic fluids.

About Prof. Doi

Masao Doi is the Chief Scientist of Interdisciplinary Center for Theoretical Study(Under the supports of the ITP, the Oujiang Laboratory and Wenzhou Institute), who is a Professor Emeritus at Nagoya University and the University of Tokyo, and was a fellow of Toyota Physical and Chemical Research Institute and the director of Center of Soft Matter Physics & its Applications, Beihang University.

Masao Doi is a leading polymer scientist who has worked on many problems in soft matter and given important contributions. He has developed fundamental theories which explain complex mechanical properties of soft matter (polymers, gels, liquid crystals, colloidal solutions etc.) from microscopic structure of the material. In his early work, he showed how the complex viscoelasticity of liquid polymer is related to the molecular structures, such as molecular weight, branching, stiffness etc. He also gave the first molecular theory for the flow of liquid crystals.

In 1978 and 1979 he wrote a series of papers with Sir Sam Edwards expanding on the concept of reputation introduced by Pierre-Gilles de Gennes in 1971. They explained the non-linear viscoelasticity of liquid polymers starting from a molecular model of polymers. The Doi-Edwards theory was the first molecular theory for viscoelasticity of the molten state of polymers which also was a scientific milestone in the field of polymer research. He has studied many problems in soft matter in non-equilibrium state, such as rheology, diffusion, phase transitions etc., and made important contributions.

Masao Doi has written 3 monographs on polymer and soft matter physics. “The theory of polymer dynamics” (coauthored with S.F. Edwards, Oxford Univ. Press, 1986)”, “Introduction to polymer physics” (OUP, 1995), and “Soft matter physics” (OUP 2013). They are extensively used by researchers and students in the world.

With these works, Masao Doi has received many interatioanl awards including Polymer prize (APS 2001) and Bingham medal (Society of Rheology 2001). He was awarded Purple Ribbon Medal in 2010. In 2015, he was awarded the prestigious Humboldt Research Award by the Alexander von Humboldt Foundation. He became a foreign member of National Academy of Engineering, USA in 2016.